Mexoryl SX

Tolerability and safety

Irritation potential

Low

Allergen risk

Low

Pregnancy

Caution

Suitable for

Normal, Dry, Oily, Combination, Sensitive

About this ingredient

Mexoryl SX is the trade name for Terephthalylidene Dicamphor Sulfonic Acid (TDSA), also known as ecamsule. Developed by L'Oréal in the 1980s as a water-soluble organic UVA filter with peak absorption at 345 nm. Covers UVA II (320–340 nm) and partially UVA I (340–400 nm). INCI: Terephthalylidene Dicamphor Sulfonic Acid. Maximum allowed concentration in sunscreens is 10% in the EU, Canada, and most of Asia. In the US it is approved under restricted use – only in specific La Roche-Posay formulas under a special FDA pathway. Photostability. Mexoryl SX is photostable, unlike classic avobenzone. Often combined with Mexoryl XL (oil-soluble fraction with wider UVA I coverage) and octocrylene for extended coverage. Pregnancy safety. As of 2026, status is caution. Systemic absorption through intact skin is low but detectable in urine after typical application (2 mg/cm² on 75% body surface). No teratogenic effects in the literature, no endocrine activity in standard assays. The caution rating reflects limited human prenatal literature. Lactation safety. Safe while breastfeeding. Systemic concentrations after topical application are below clinically meaningful thresholds. Skin safety. Low irritation and low allergen risk. Suitable for sensitive skin and patients with photodermatoses. Non-comedogenic. Compared with Tinosorb S. Tinosorb S covers a wider range (full UVB+UVA) and is often more efficient per unit concentration. Modern French sunscreens in the L'Oréal group (La Roche-Posay, Vichy) combine both filters for optimal coverage. Bottom line. Mexoryl SX is a time-tested UVA filter with good photostability and a low irritation profile. The caution flag in pregnancy is a precautionary stance rather than a sign of harm.

Frequently asked questions