Mexoryl SX: Comedogenic Rating & Ingredient Analysis
Mexoryl SX, whose INCI name is ecamsule, is a patented sunscreen filter developed by L'Oreal that helped define modern UVA protection. It is a photostable, water-soluble filter that targets short-wavelength UVA, the range that avobenzone covers less strongly, so the two are often combined for complete UVA defence. Mexoryl SX has an unusual regulatory story: it has been used in Europe since the 1990s, but in the United States it is approved only within specific L'Oreal-owned products that went through the FDA's new-drug approval process, rather than as a generally available filter.
Quick facts
- Comedogenic rating
- our estimate — not measured
- Irritation risk
- Low
- Effective pH
- —
- Typical strength
- EU ≤10%
- Pregnancy
- Considered safe
- Suits skin types
- oilydrycombinationsensitivenormalacne-pronemature
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 | 7/7 |
| 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 | EU ≤10% |
What is it?
Ecamsule is a water-soluble organic filter with peak absorption around 345 nanometres, covering short UVA especially well. It is notably photostable, so it maintains protection through sun exposure, and because it is water-soluble it behaves differently in formulas from oil-soluble filters, often used in the water phase. It was one of the filters measured in the FDA's 2019 maximal-use absorption study, where systemic levels were detected but remained a subject for further data rather than a safety verdict. In practice Mexoryl SX is paired with UVB filters and with its oil-soluble sibling Mexoryl XL to build broad, stable protection.
Benefits
Strong short-UVA coverage
Ecamsule absorbs short-wavelength UVA particularly well, complementing avobenzone and rounding out protection across the full UVA range.
Photostable
It holds up well in sunlight rather than degrading quickly, giving dependable protection against the wavelengths that drive pigmentation and aging.
Water-soluble flexibility
Being water-soluble lets formulators build it into the water phase for light, comfortable textures that suit sensitive and acne-prone skin.
Proven in dermatology
It has decades of European use and appears in dermatologist-recommended lines, often combined with mexoryl-xl and antioxidants like vitamin-e.
How to use
Mexoryl SX comes formulated into finished sunscreens, particularly from L'Oreal-owned brands; use them as your daily broad-spectrum SPF, applied generously and reapplied every two hours in sun. Because ecamsule focuses on short UVA, it works best alongside avobenzone and UVB filters, so choose a broad-spectrum product. It layers well under makeup and over antioxidant serums with vitamin-c. In the US you will find it only in specific branded products rather than across the market, so read labels if you are seeking it out.
Side effects
Mexoryl SX is well tolerated, with low irritation and contact-allergy rates. It was among filters detected in blood in the FDA's absorption testing, which the agency flagged for more study without declaring it unsafe, and it continues to be used widely in Europe. As with any sunscreen, keep it away from the eyes. There is no established evidence of harm at normal cosmetic use.
Who should avoid it
No group specifically needs to avoid Mexoryl SX; it is gentle and generally considered acceptable in pregnancy. US availability is limited to particular products because of its approval pathway. Anyone with a rare allergy to it should use a mineral sunscreen with titanium-dioxide instead.
Pairs well with
Frequently asked questions
What is ecamsule?
Ecamsule is the INCI name for Mexoryl SX, a photostable, water-soluble short-UVA sunscreen filter developed by L'Oreal and used widely in Europe since the 1990s.
Is Mexoryl SX available in the US?
Only within specific L'Oreal-owned products approved through the FDA's new-drug process, not as a generally available filter that any brand can use.
Does Mexoryl SX replace avobenzone?
Not exactly. It covers short UVA especially well and is often combined with avobenzone, which covers longer UVA, for complete UVA protection.
Is Mexoryl SX safe?
It is well tolerated and widely used in Europe. It appeared in the FDA's absorption study, which prompted more data requests but not a finding of harm.
Sources & further reading
Medical disclaimer
Find your personal acne triggers
Our free Acne Tracker lets you log breakouts, sleep, stress and diet, and shows you which factors correlate with your flare-ups.