Serine: Comedogenic Rating & Ingredient Analysis
Serine is one of the most abundant amino acids in the skin's natural moisturising factor, so it is a genuinely native hydrating ingredient rather than a borrowed one. Its main job in skincare is to help the surface hold onto water, keeping it soft, smooth and comfortable. Because it is a component the skin naturally uses to stay hydrated, serine slots seamlessly into gentle, moisturising formulas and is often combined with other amino acids like glycine and proline to mirror the mixture skin makes on its own. It is non-irritating, non-comedogenic and a reliable, low-key hydrator suited to every skin type.
Quick facts
- Comedogenic rating
- our estimate — not measured
- Irritation risk
- Low
- Effective pH
- —
- Typical strength
- 0.1–2%
- Pregnancy
- Considered safe
- Suits skin types
- drysensitivenormalcombinationmatureacne-prone
Where this number comes from
No one has published a comedogenic rating for this ingredient. Fulton's 1989 table tested about 250 raw materials and this was not among them, and we found no later study measuring it. The figure shown is our own reasoning from the ingredient's chemistry and how it is used — treat it as an estimate, not a measurement.
Fulton read his own scale as 0-1 not significant, 2-3 borderline, 4-5 positive. The assay is the rabbit ear at 10% dilution, which the paper itself calls extremely sensitive and not fully predictive of human skin. Ratings describe the raw ingredient; concentration and formulation change real-world behaviour.
Caution profile
The four published fields on this page, on one 0–5 scale. Further from the centre means more care is needed — never that the ingredient is worse.
Derived, not measured: pore-clogging is the published comedogenic rating; irritation maps low/moderate/high to 1/3/5; pregnancy maps safe/caution/avoid to 0/3/5; skin-type limits is how many of the seven skin types this entry does NOT list. Every input is printed in words in the quick-facts card above.
Show the numbers
| Metric | 0–5 | Published field |
|---|---|---|
| Pore-clogging | 0 | 0/5 |
| Irritation | 1 | Low |
| Skin-type limits | 0.7 | 6/7 |
| Pregnancy | 0 | Considered safe |
Working pH and typical strength
Where this ingredient is formulated to sit, and at what concentration.
Both bars come from the fields above: the pH window and the typical strength range published for this ingredient. The tinted column is healthy skin's surface pH (about 4.7–5.75).
Show the numbers
| Metric | 0–5 |
|---|---|
| Typical strength | 0.1–2% |
What is it?
Serine (L-serine) is a small amino acid that is one of the largest contributors to the skin's natural moisturising factor (NMF), the internal blend of water-attracting molecules living skin cells accumulate to stay supple. When the skin barrier and NMF are healthy, serine and its fellow amino acids hold water in the stratum corneum and keep the surface flexible; when they run low, skin feels dry and rough. Applying serine tops up this reservoir, supporting hydration and a conditioned feel. It is also mildly antistatic and smoothing. Serine is part of the same family of ingredients as glycine, proline and arginine, and formulas often use a blend to recreate NMF. It is non-comedogenic and very well tolerated.
Benefits
Replenishes moisture factor
As one of the most abundant amino acids in NMF, serine tops up the skin's own water-binding reservoir for lasting surface hydration.
Softens and smooths
It conditions the surface, easing dryness and roughness and leaving skin feeling supple and comfortable.
Works in an amino-acid blend
Serine pairs with glycine, proline and other amino acids to mirror the skin's natural moisturising mixture for balanced hydration.
Gentle for all skin
Serine is a molecule the stratum corneum already stocks in quantity, so at a rating of 0 there is nothing for reactive or acne-prone skin to object to — you are topping up a native ingredient, not introducing a foreign one.
How to use
Use products with serine as directed, morning or night. Like other humectant amino acids, it works best applied to slightly damp skin and followed with a moisturiser so the water it helps bind is sealed in. Serine is at home in soothing and barrier-focused routines, layered with fellow amino acids like glycine and proline and with humectants such as hyaluronic acid. It requires no adjustment period, does not increase sun sensitivity and is compatible with the common actives you might use alongside it.
Side effects
Serine is very well tolerated on the skin, with irritation and allergy being rare, as it is a molecule the skin naturally contains. Its comedogenic rating is 0, and being one of NMF's own components it does nothing to alter how the surface responds to UV. As with all humectants, in very dry air it should be sealed with an occlusive so it does not draw moisture to the surface to evaporate. For nearly all users it is comfortable and uneventful.
Who should avoid it
No skin type needs to avoid topical serine. Those with very dry skin should pair it with richer moisturisers rather than using humectants alone. People with a rare amino-acid sensitivity can patch test first.
Pairs well with
Frequently asked questions
What does serine do for skin?
It hydrates and conditions the surface as one of the most abundant amino acids in the skin's natural moisturising factor, keeping skin soft, smooth and comfortable.
Is serine good for dry skin?
Yes. Because serine is a major part of the skin's own moisturising factor, replenishing it topically supports hydration and helps relieve the tightness and roughness of dry skin.
Does serine clog pores?
No. Serine has a comedogenic rating of 0 and is a small water-soluble amino acid, so it does not clog pores and suits acne-prone skin.
Should serine be combined with other amino acids?
Often, yes. Formulas commonly blend serine with glycine, proline and others to recreate the skin's natural mixture of moisturising amino acids for more balanced hydration.
Sources & further reading
Medical disclaimer
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