Tag: moisturiser

  • 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

  • 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