Tag: ceramides

  • Why Skin Dries in Autumn: Three Seasonal Studies in Korean Skin, and the Two Measures That Did Not Move (Autumn Guide 2)

    Cover image for an autumn guide to why skin dries in Korea, the second autumn guide from Dr. J Ingredient Notes. Three seasonal studies in Korean skin found that moisture and scaliness move with the season while wrinkles do not.

    🇰🇷 한국어판: 가을 피부 건조, 계절 연구가 보여 준 것 (가을 특집 2)

    Hello, this is Dr. J. Autumn is when the shelf gets rearranged — a heavier cream, a richer cleanser, something for the flaking. Before changing anything, it is worth asking a narrower question: what does the season actually change in skin, and what does it leave alone?

    Three studies measured exactly that in Korean skin, in Korea. Two followed people across the seasons; one looked at a single heated day indoors. Read together they draw a fairly clear line between the measures that move and the measures that do not.

    That line is the useful part, because it tells you which half of your routine the season is arguing with.

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    The studies, if you would rather read them first

    📄 Nam GW et al., Skin Res Technol 2015;21(1):1-8 — 89 Korean women, 13 months

    📄 Song EJ et al., Int J Cosmet Sci 2015;37(1):92-97 — 100 Korean men, summer and winter

    📄 Park EH et al., Skin Res Technol 2023;29(6):e13397 — six hours in a heated room

    All three were carried out in Korea on Korean participants. Seasonal work travels badly between climates, so that is the ground this article stands on.

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    Five lines, if you are in a hurry

    ✔ Over 13 months, scaliness rose as temperature, humidity and rainfall fell

    ✔ Outdoor relative humidity in that period ran from 46% in February to 75% in July and August

    ✔ In 100 men measured twice, moisture differed between summer and winter at every site

    ✔ Six hours in a heated room raised facial roughness and redness, and water loss on the forearm

    ✔ Wrinkles and brightness did not change with the season — which is where this article turns

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    Three studies, three designs

    The three were built differently, and that is a strength rather than a weakness: one followed the same people for over a year, one sampled two seasons, and one watched a single day indoors.

    Study Who How long Where measured
    Nam et al. 2015
    Skin Res Technol    		 89 Korean women
    mean age 29.7    		 13 months, continuously Forehead, under-eye, front cheek, eye corner, side cheek, inner forearm — six sites
    Song et al. 2015
    Int J Cosmet Sci    		 100 Korean men
    aged 20 to 59    		 Summer and winter, once each Forehead, cheek, arm, glabella, nose wing, eye corner
    Park et al. 2023
    Skin Res Technol    		 Participant number not given in the abstract Heated indoor room, over 6 hours a day Face (randomised split-face) and forearm

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    Thirteen months of measurements

    The first study tracked 89 women and set their skin measurements beside the weather of the same period — temperature, humidity, atmospheric pressure, hours of sunshine and rainfall. That is what makes it more useful than a general statement that winter is drying.

    Outdoor conditions measured Lowest Highest
    Temperature −1.7 °C in January 26.5 °C in August
    Relative humidity 46% in February 75% in July and August

    Across the year that is a span of roughly 28 degrees and 29 percentage points of humidity. And the findings followed those curves:

    ✔ Scaliness rose as temperature, humidity and rainfall fell, and moved the opposite way to atmospheric pressure and sunshine hours

    ✔ Elasticity was higher when temperatures were higher

    Autumn sits on the downslope of the humidity curve rather than at its bottom. February is the low point, but the descent begins months earlier — which is why flaking tends to arrive before deep winter does.

    ※ A correlation means the two moved together. The study did not claim that falling humidity caused the scaliness, and neither will I.

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    Summer against winter, in 100 men

    The second study measured a different population — men, a wider age range, a different design — and pointed the same way.

    Measure Seasonal difference Which season was higher
    Moisture Significant at every site Varied by site between the two seasons
    pH Yes Higher in winter
    Sebum Yes Higher in summer
    Sensitivity Yes Higher in winter
    Pores Yes More prominent in summer
    Wrinkles and brightness No No difference between the seasons

    Lay the two studies on top of each other and the season’s territory narrows to moisture, scaliness and sensitivity. Two groups differing in sex and age pointed the same way, which is worth more than either result alone.

    Chart of what three seasonal studies in Korean skin measured. First, 89 Korean women of mean age 29.7 were measured at six sites for 13 months; outdoor air ran from minus 1.7 degrees Celsius in January to 26.5 in August and relative humidity from 46 percent in February to 75 percent in July and August, and scaliness rose as temperature, humidity and rainfall fell, Nam and others, Skin Research and Technology 2015. Second, 100 Korean men aged 20 to 59 were measured in summer and in winter; moisture differed between the seasons at every site measured, pH was higher in winter and sebum higher in summer, sensitivity rose in winter and pores stood out in summer, while wrinkles and brightness showed no seasonal difference, Song and others, International Journal of Cosmetic Science 2015. Third, in a randomised split-face trial with a ceramide cream on one side only, six hours in a heated room raised facial skin temperature, pores, roughness, redness and wrinkles, and water loss rose on the forearm, with the number of participants not given in the abstract, Park and others, Skin Research and Technology 2023.

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    What the season did not change

    The most useful line in that table is the last one. Wrinkles and brightness showed no seasonal difference.

    Those are the two things people tend to report in autumn — skin looks older, skin looks duller. Measured across two seasons, neither moved. What moved was moisture, scaliness and sensitivity.

    So the shelf rearrangement sorts itself out. The water and barrier half of a routine is what the season is arguing with; the wrinkle and brightness half can carry on unchanged. Swapping a retinoid or a brightening serum because the calendar turned is answering a question the data did not ask.

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    Six hours in a heated room

    Outdoor weather is only half of it. In autumn and winter we spend the day in heated rooms, and one trial looked straight at that.

    Participants spent more than six hours a day in a heated indoor environment. The design was randomised split-face: a ceramide cream on one side of the face, nothing on the other, so each person served as their own control.

    ✔ After six hours the face showed higher skin temperature, pores, roughness, redness and wrinkles

    ✔ On the forearm, transepidermal water loss rose — the arm registers it before the face does

    ✔ The paper’s conclusion recommends a ceramide-containing cream for long winter days indoors

    ※ The number of participants is not stated in the abstract, so I have left it out rather than guess.

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    Three changes that follow from the data

    ✔ Keep out of the direct path of a heater — that is the condition the six-hour trial tested

    ✔ Apply before the skin dries after washing, and start with arms and legs, which show it first

    ✔ Choose by tightness, roughness or stinging — those are the three the season actually moved

    What you notice The measure that moved Where to look
    Tightness Moisture (Song 2015) Humectants — glycerin, hyaluronic acid
    Roughness, flaking Scaliness (Nam 2015) Keratolytic humectants — urea
    Stinging, redness Sensitivity (Song), redness (Park) Barrier lipids — ceramides, panthenol

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    Reading the numbers carefully

    ✔ Correlation is not cause. Scaliness moved against humidity; the study did not say humidity produced it

    ✔ Climate and year change the figures. 46% in February is what that study recorded in that period, not a constant

    ✔ I quoted only what the abstracts confirm. Where a detail is missing, such as the participant count in the 2023 trial, it stays missing here

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    What I left out, and why

    ✔ Indoor humidity guidance. The Korean legal databases were unreachable while this was written, so I did not quote an indoor standard. Every humidity figure here is outdoor, as measured by the studies

    ✔ The mechanism linking humidity to barrier function. That would have been a second-hand citation from a review, so it is out

    ✔ This year’s weather data. It varies by region and year; I kept to the periods the studies measured

    ✔ Product names. This blog does not recommend particular products

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    In one line

    The season moved moisture, scaliness and sensitivity, and left wrinkles and brightness alone. That is where an autumn routine has something to answer.

    Next in this series: Korea’s rules for children’s cosmetics — what a label saying “for children” sets in motion, and why the box then prints a preservative percentage (Ingredient Guide 20).

    📌 Earlier guides

    📌 Ceramides: the Cholesterol and Fatty Acid Ratio (Guide 4)

    📌 Panthenol: What the Dexpanthenol Studies Show (Guide 7)

    📌 Hyaluronic Acid: How to Read the Molecular Weight (Guide 6)

    📌 How to Read a Korean Cosmetic Ingredient List (Guide 14)

    About the author · Dr. J

    MS in Veterinary Medicine, PhD in Life Sciences. I worked as a researcher at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) and now run Beaurea, a cosmetics manufacturing company, where I write the formulas myself. This blog reads the research papers and the regulatory documents and turns them into plain-language criteria for choosing ingredients. I don’t recommend specific products here – only criteria that apply to any product.

    📄 References

    · Nam GW, Baek JH, Koh JS, Hwang JK, Skin Res Technol 2015;21(1):1-8

    · Song EJ et al., Int J Cosmet Sci 2015;37(1):92-97

    · Park EH et al., Skin Res Technol 2023;29(6):e13397

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    This article summarises published research and is not a substitute for diagnosis or treatment. The figures are those confirmed in each paper’s abstract, and results shift with the climate and the period measured. If something about your skin worries you, please speak to a professional.

    — Dr. J Ingredient Notes

  • Moisturizing Ingredients for Dry Skin: What the Research Shows for Five of Them (Autumn Guide)

    Cover image for a Dr. J Ingredient Notes autumn guide on moisturizing ingredients for dry skin. Five ingredients with human studies: glycerin, urea, ceramides, panthenol and hyaluronic acid, with what each number was compared with.

    🇰🇷 한국어판: 건조한 피부 보습 성분 TOP5 – 가을에 고르는 기준

    Hello, I’m Dr. J. Autumn is when the same question arrives every year: which moisturizing ingredients actually do something for dry skin? Here are five, each with a human study attached, and each with the numbers read the way I would read them in the lab.

    This is not a ranking. The five do different jobs, and the one you want depends on what your skin does after cleansing: tightness, roughness and flaking, or stinging. Match that first and the shelf gets much smaller.

    Below: one table with all five studies side by side, then each ingredient in turn, then the part most ingredient articles skip — what each number was compared with, because “improved by 72%” and “better than placebo” are not the same claim. At the end, how Korean regulation treats these five, and why squalane is not among them.

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    📄 If you’d rather read the primary sources

    📄 Lodén et al. 2002 — glycerin 20% and urea 4% creams, 197 patients, 30 days (Acta Derm Venereol)

    📄 Spada et al. 2021 — ceramide-dominant cream and cleanser, 28-day randomized trial (Dermatol Ther)

    📄 Stettler et al. 2021 — panthenol emollients, three 28-day studies (open access)

    📄 Pavicic et al. 2011 — hyaluronic acid 0.1%, 76 women, 60 days (PubMed)

    📄 Korea — Cosmetic Safety Standards, Annex 2: ingredients with use limits (Korean)

    The Stettler paper is fully open, tables included. The Korean annex downloads as the original table.

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    The short version

    ✔ Tight skin — humectants that hold water: glycerin, hyaluronic acid

    ✔ Rough, flaking skin — urea, capped at 10% in cosmetics sold in Korea

    ✔ Stinging after cleansing — barrier ingredients: ceramides, panthenol

    ✔ All five have human studies of one to two months

    ✔ Before trusting a percentage, ask what it was compared with (Table 2)

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    All five studies in one table

    Ingredient Study People · duration Compared with What was measured
    Glycerin 20% Lodén et al. 2002 68 of 197 · 30 days the same cream without glycerin dryness improved in 85% (placebo 63%)
    Urea 4%
    with 4% sodium chloride    		 Lodén et al. 2002 63 in the same study · 30 days the other creams in that study improved in 89%; smarting in 24%
    Ceramides Spada et al. 2021 100 adults (83 completed) · 28 days a comparator regimen · double-blind water loss P=.0342; hydration P<.0001
    Panthenol Stettler et al. 2021 42 people × 3 studies · 28 days the untreated opposite arm hydration +38.1% to +72.4% vs baseline
    Hyaluronic acid 0.1% Pavicic et al. 2011 76 women · 60 days placebo all five molecular weights improved hydration

    Read the “compared with” column first. It is the column that decides how much weight each number can carry, and it is the one marketing copy leaves out.

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    1 and 2. Glycerin and urea — measured in the same study

    In this trial, 197 patients with atopic dermatitis used one of three creams at least once a day for 30 days (Lodén et al., Acta Derm Venereol 2002):

    ✔ a cream with 20% glycerin — 68 people

    ✔ the same cream base without glycerin, as placebo — 66 people

    ✔ a cream with 4% urea and 4% sodium chloride — 63 people

    After 30 days, dermatologist-assessed dryness had improved in 85% of the glycerin group, 63% of the placebo group and 89% of the urea group. Taking the patients’ own assessments together with the dermatologist’s, the paper’s conclusion is that the glycerin cream and the urea-saline cream had equal effects on dryness.

    What separated them was how they felt. Smarting — that brief sting on application — was rated severe or moderate by 10% of people on the glycerin cream and 24% on the urea-saline cream (p<0.0006). For stinging, itching and dryness/irritation as separate reactions, the paper reports no differences.

    That is why I treat urea as an ingredient to choose on calm days, and why it earns its place on heels, elbows and anywhere the skin is genuinely thickened rather than simply dry.

    ※ The participants had atopic dermatitis. I am quoting the dryness and sensory results, not treating this as a treatment claim. The creams were supplied by the manufacturer (Aco Hud AB).

    Evidence figure for five moisturizing ingredients. First, in 197 patients using creams for 30 days, dermatologist-assessed dryness improved in 85 percent with 20 percent glycerin versus 63 percent with the same cream without glycerin, Loden and colleagues, Acta Dermato-Venereologica 2002. Second, in the same study, 4 percent urea with 4 percent sodium chloride improved dryness in 89 percent, but smarting was rated moderate or severe by 24 percent versus 10 percent for glycerin; Korea caps urea at 10 percent. Third, a ceramide-dominant cream and cleanser used by 100 adults with moderate eczema for 28 days reduced water loss, P equals .0342, and raised hydration, P below .0001, while eczema severity did not differ between groups, Spada and colleagues 2021. Fourth, panthenol emollients used once daily for 28 days by 42 people in each of three studies raised hydration from baseline by 38.1 to 72.4 percent while the untreated arm stayed unchanged, Stettler and colleagues 2021. Fifth, hyaluronic acid at 0.1 percent in five molecular weights used by 76 women for 60 days improved hydration versus placebo, Pavicic and colleagues 2011.

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    3. Ceramides — the barrier numbers move first

    A ceramide-dominant cream used together with a matching cleanser for 28 days, in a randomized, double-blind trial of 100 adults with moderate eczema, 83 of whom completed it (Spada et al., Dermatol Ther 2021).

    ✔ Transepidermal water loss fell compared with the comparator (P=.0342)

    ✔ Stratum corneum hydration rose compared with the comparator (P<.0001)

    ✔ Eczema severity (EASI) showed no difference between the groups (P=.7804)

    ✔ Satisfaction with itch, dryness and smoothness was higher on the ceramide regimen

    The third line is the honest one, and it is why I like this study. The barrier measurements moved; the disease score did not. A moisturizer is a moisturizer. Ceramides also work as part of a set — with cholesterol and fatty acids — which is the subject of the ceramide guide linked at the end.

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    4. Panthenol — once a day, 28 days

    Three parallel studies of panthenol-containing emollients that differed in lipid content: low, intermediate and high. Each had 42 participants applying the product to one forearm once daily for 28 days, leaving the other forearm untreated (Stettler et al., Cosmetics 2021).

    At day 28, hydration had risen from baseline by 63.9% (low lipid), 72.4% (intermediate) and 38.1% (high). On the untreated arm, hydration did not move — which is what makes the rise hard to attribute to the weather.

    Two caveats travel with those percentages: they are measured against baseline, not against a panthenol-free cream, and they belong to the whole formulation, which also contained lipids such as shea butter and squalane. The full reading of this study is in the panthenol guide.

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    5. Hyaluronic acid — five molecular weights in one study

    Creams with 0.1% hyaluronic acid at five different molecular weights, used by 76 women for 60 days against placebo (Pavicic et al., J Drugs Dermatol 2011). All five improved hydration relative to placebo.

    So on a label, what I look for is more than one molecular weight listed, rather than a single impressive-sounding number. How to read those numbers is covered in the hyaluronic acid guide.

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    How to read the numbers — the comparator decides the meaning

    The five studies did not use the same yardstick. Here is what each comparison can and cannot tell you.

    Comparator Used here by How to read the number
    The same cream minus one ingredient glycerin The closest thing to what that ingredient added
    A different product ceramides A product-versus-product result, not one ingredient
    Untreated skin panthenol The whole cream versus applying nothing
    Day 0 (baseline) the panthenol percentages Season and humidity ride along; check whether untreated skin was measured too
    Placebo hyaluronic acid Same formula, different ingredient

    The strongest design here is the same cream with one ingredient removed: formulation held constant, so the difference is attributable to the ingredient. The weakest, in this sense, is a percentage against baseline, because the season is inside that number — unless, as in the panthenol studies, untreated skin was measured alongside and stayed flat.

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    How Korea regulates these five

    One of the five appears in Annex 2 of the Cosmetic Safety Standards — the list of ingredients with use limits.

    Korea What that means on a label
    Urea listed in Annex 2 of the Cosmetic Safety Standards at 10% (CAS 57-13-6) A product sold in Korea stays at or below 10%
    Glycerin · ceramides · panthenol · hyaluronic acid not in that annex No ceiling, and no minimum either — concentration varies by product
    Brightening · anti-wrinkle ingredients listed with set amounts in Annex 4 of the functional-cosmetics review rules Moisturizing ingredients are not in that kind of table

    This is worth knowing when you compare a Korean product with one from elsewhere. Korea sets a ceiling for urea at 10%; the study above used 4%, well inside it. For the other four, there is no number in the regulation at all — no maximum, and equally no minimum, which is why the ingredient list’s order matters more than any claim on the front of the bottle.

    It is also why moisturizing ingredients are not “functional cosmetics” in the Korean sense. Brightening and anti-wrinkle ingredients have an annex listing set amounts; hydration does not work that way.

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    Why squalane is not on this list

    Squalane comes up in every autumn skincare article, so I went looking again. I could not find a study in which squalane was applied to human skin and its hydration effect compared with a placebo. What exists is work outside the body — an ex vivo study of how a squalane-based emulsion carries other compounds into skin, and a cell study of squalane and UV-related collagen effects in fibroblasts.

    That is not evidence of absence; it is a statement about what I could verify. If I find a human trial, squalane gets its own guide.

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    Five things to check on the label

    ✔ Glycerin — near the top of the ingredient list; higher means more of it

    ✔ Urea — if a percentage is printed, 10% or below, and start low

    ✔ Ceramides — cholesterol and fatty acids listed alongside them

    ✔ Panthenol — for a cream you will use on stinging days, fragrance low on the list or absent

    ✔ Hyaluronic acid — more than one molecular weight listed

    My own order is simple. If tightness comes first after cleansing, I reach for the water-binding side. If stinging comes first, I reach for the barrier side. If both, one product containing both is a reasonable place to start.

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    In one line

    Tight skin: glycerin and hyaluronic acid. Rough skin: urea. Stinging skin: ceramides and panthenol. Start from what your skin does, and read every percentage together with what it was compared against.

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    📌 Earlier guides

    📌 Ceramides – the cholesterol and fatty acid ratio (Ingredient Guide 4)

    📌 Panthenol for Skin: What the Dexpanthenol Studies Show (Ingredient Guide 7)

    📌 Hyaluronic Acid: How to Read the Molecular Weight (Ingredient Guide 6)

    📌 How to Read a Korean Cosmetic Ingredient List — Where the Order Stops at 1% (Ingredient Guide 14)

    About the author · Dr. J

    MS in Veterinary Medicine, PhD in Life Sciences. I worked as a researcher at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) and now run Beaurea, a cosmetics manufacturing company, where I write the formulas myself. This blog reads the research papers and the regulatory documents and turns them into plain-language criteria for choosing ingredients. I don’t recommend specific products here – only criteria that apply to any product.

    📄 References

    · Lodén M, Andersson AC, Anderson C, et al. Acta Derm Venereol 2002;82(1):45-47

    · Spada F, Harrison IP, Barnes TM, et al. Dermatol Ther 2021;34(4):e14970

    · Stettler H, de Salvo R, Olsavszky R, et al. Cosmetics 2021;8(1):18

    · Pavicic T, Gauglitz GG, Lersch P, et al. J Drugs Dermatol 2011;10(9):990-1000

    · Korea MFDS — Regulation on Safety Standards for Cosmetics, Annex 2 (ingredients with use limits)

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    This article summarises published research and safety assessments. It is information, not a diagnosis or a treatment plan. If something about your skin worries you, please talk to a professional.

    — Dr. J Ingredient Notes

  • Ceramides Work Better With Company – What 4 Studies Say About the Back of the Jar (Ingredient Guide 4)

    Cover image for Ceramides Work Better With Company. Dr. J Ingredient Notes guide 4, summarising four studies showing that skin barrier repair was faster when ceramide, cholesterol and fatty acid were applied together.

    Hello, this is Dr. J.

    The fourth ingredient guide is about ceramides.

    Every year, as soon as the air turns dry, the same question arrives: which moisturiser should I be using?

    Here is the part that makes the answer interesting. In a 1996 experiment, skin treated with ceramides on their own repaired its barrier at a different speed from skin treated with ceramides alongside two other lipids. Same ingredient, opposite direction.

    Today I will follow that thread and end up at the back of the jar.

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    📄 Read the sources first, if you prefer

    · Man MQ et al., J Invest Dermatol 1996 – barrier repair timed as the lipid ratio was varied

    · Tanno O et al., Br J Dermatol 2000 – niacinamide and ceramide synthesis

    · 🏠 COSMILE Europe INCI database – type an ingredient name from your label and read what it is

    The abstracts carry the exact ratios and time points I have left out here. Open them above if you want them.

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    Fifteen-second summary · no sound

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    The four lines, if you are in a hurry

    ✔ Ceramides are the lipids that fill the space between skin cells. When they run low, water leaves

    ✔ Barrier repair was faster with cholesterol and fatty acid present than with ceramides alone

    ✔ In studies of 24 children and 100 adults, water loss through the skin came down

    ✔ Niacinamide raised the skin’s own ceramide production 4.1 to 5.5 fold

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    Why ceramides alone were slower – the 1996 ratio experiment

    Picture the outer layer of skin as a brick wall. The cells are the bricks, and the mortar filling the gaps is made of three things: ceramides, cholesterol and fatty acids. Mortar only sets when all three are mixed. Pour in as much sand as you like – without cement and water it never hardens.

    Man MQ and colleagues published the experiment in the Journal of Investigative Dermatology in 1996 (volume 106, pages 1096–1101). They disrupted the barrier deliberately, applied lipids, and timed how quickly it recovered.

    ✔ One or two of the three lipids made recovery slower, not faster

    ✔ All three in equal parts restored normal speed, and a 3-fold excess of any one made it quicker still

    ✔ Confirmed in an animal model, and pointing the same way in disrupted human skin

    So a formula built around a single lipid is not the stronger formula. Which is why the useful question at the shelf is not whether a cream contains ceramides, but what the ceramides were formulated with.

    Evidence summary for ceramides. Shows that ceramide, cholesterol and fatty acid applied together restored normal barrier repair in a 1996 study, alongside a 24-child 20 to 21 week study, a 100-adult 28-day randomised controlled study, and a 2000 study in which niacinamide raised ceramide synthesis 4.1 to 5.5 fold.

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    Did it hold up in people – 24 children, 100 adults

    Chamlin SL and colleagues, Journal of the American Academy of Dermatology 2002, volume 47, pages 198–208.

    Twenty-four children with atopic dermatitis added a ceramide-dominant product to their routine for 20 to 21 weeks. By week three, 22 of the 24 had lower severity scores, and water loss through the skin kept falling even after the scores had levelled off. The visible part settled first; the barrier itself carried on mending underneath.

    Spada F and colleagues, Dermatologic Therapy 2021, volume 34, e14970.

    One hundred adults were randomised for 28 days, one group using a ceramide-dominant cream and cleanser. Water loss and skin hydration both did better than in the control group, and ratings for itch and dryness were higher as well.

    The two products share one thing. Ceramides sat at the centre of the formula, with cholesterol and fatty acids beside them. You do not need the product names. The shape of the combination is the part worth carrying to the shop.

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    Finding the names on the label – five lines that decide it

    Ceramides appear under several names. These are the five lines to look for.

    What you will see on the label Which of the three it belongs to
    Ceramide NP · AP · EOP · NG · AS The ceramides themselves. The letters describe structure, not grade
    Hydroxypalmitoyl sphinganine · Phytosphingosine Same family, listed under a different name
    Cholesterol The second ingredient in the 1996 experiment
    Stearic acid · Palmitic acid · Linoleic acid The fatty acid side. The third one
    Niacinamide Not a refill. It helps skin make its own

    The letters after a ceramide – NP, AP, EOP and the rest – describe molecular structure. They are not a quality ranking, and I have not found human studies comparing them head to head. Rather than picking between them, check whether cholesterol and a fatty acid are listed nearby.

    If a name is unfamiliar, type it into the COSMILE Europe INCI database and you will get its definition and function.

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    Helping skin make its own – niacinamide

    Tanno O and colleagues, British Journal of Dermatology 2000, volume 143, pages 524–531.

    Cultured human skin cells given niacinamide for six days produced 4.1 to 5.5 times more ceramides. Fatty acids rose 2.3 fold and cholesterol 1.5 fold at the same time – all three mortar ingredients together.

    Applied to skin, it also raised ceramide and fatty acid levels in the outer layer and reduced water loss. That is the reason so many jars now carry both the refill and the prompt in one formula.

    How to read a niacinamide percentage is covered in Ingredient Guide 1, on retinol, where the same approach to concentration numbers applies.

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    When to apply it – order and combinations

    ✔ Straight after cleansing, while skin is still slightly damp, is the easiest moment

    ✔ On retinol or AHA nights, put it on last. That is the night it earns its place

    ✔ There is no need to separate it from a vitamin C serum. Serum first, cream after

    ✔ With anything new, try it on the inner forearm and give it two days

    👉 If layering order gets confusing, the ingredient compatibility chart covers twelve ingredients and what to keep apart.

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    Five things to check before you buy

    ✔ Are they together? Cholesterol and a fatty acid listed alongside the ceramides

    ✔ Where on the list? Ceramides near the front or middle rather than the very end

    ✔ Is niacinamide there? The refill and the prompt in one jar

    ✔ Does the texture suit your week? In dry months a cream or balm holds up better than a lotion

    ✔ Where does fragrance sit? High on the list is worth noticing when the barrier is already stressed

    Save these five lines and open them at the shelf. Reading the back of a jar takes about five minutes.

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    In one line

    🧪 Ceramides look most like the research when cholesterol and a fatty acid are in the formula and niacinamide is nearby.

    The next ingredient guide is collagen – what changes between putting it on your skin and taking it by mouth.

    📌 Earlier posts

    · Skincare Ingredient Compatibility Chart – 12 ingredients, what to layer and what to split

    · Retinol: Start at 0.1% – how to read the concentration numbers

    · Not All Vitamin C Serums Work – 3 conditions the research says you need

    About the author · Dr. J

    MS in Veterinary Medicine, PhD in Life Sciences. I worked as a researcher at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) and now run Beaurea, a cosmetics manufacturing company, where I write the formulas myself. This blog reads the research papers and the regulatory documents and turns them into plain-language criteria for choosing ingredients. I don’t recommend specific products here – only criteria that apply to any product.

    📄 References

    · Man MQ et al., J Invest Dermatol 1996;106(5):1096-1101

    · Chamlin SL et al., J Am Acad Dermatol 2002;47(2):198-208

    · Spada F et al., Dermatol Ther 2021;34(4):e14970

    · Tanno O et al., Br J Dermatol 2000;143(3):524-531

    · 🏠 COSMILE Europe INCI database

    Note: this article reads the research and sets out criteria for choosing an ingredient. It does not recommend a particular product. What suits you depends on your skin and on what you already use, so try anything new on the inner forearm first.


    Dr. J Ingredient Notes | Ingredient Guide 4 · Ceramides