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Terephthalylidene Dicamphor Sulfonic Acid

Water-soluble UVA filter (Mexoryl SX) from L'Oréal is one of the best protectors in the long-wave UVA range. Its unique ability to protect against UVA-I (340–400 nm) makes it the foundation of the premium photoprotection lines La Roche-Posay and Anthelios.

UVA filterMexoryl SXWater-solubleUVA-I protection

✓ Safe

Comedogenic Rating

0/5

Irritation Potential

0/5

What is it?

Terephthalylidene Dicamphor Sulfonic Acid (trade name Mexoryl SX) is a synthetic water-soluble UV filter. Patented and developed by L'Oréal Group in the 1980s. Allowed: EU (up to 10%), Canada, Australia, Japan. USA: FDA approved in 2006 only for L'Oréal products (OTC drug). UVA spectrum: absorbs 290–400 nm, maximum ~345 nm → particularly effective against UVA-I (340–400 nm), which penetrates the skin the deepest. Water-soluble → easily incorporated into the aqueous phase of formulations. Photostable — does not degrade under UV radiation.

Premium sunscreens (La Roche-Posay Anthelios, L'Oréal), daily moisturizers with UVA protection, SPF products for the face with broad spectrum.

Key Benefits

✦

The best protection against UVA-I — the most penetrating UVA

UVA-I (340–400 nm) — the longest UVA waves that penetrate through glass, clouds, and the dermis, causing photoaging and increasing the risk of melanoma. Mexoryl SX covers this range better than most other UVA filters, including avobenzone (peak ~360 nm, less stable) and butyl methoxydibenzoylmethane. This is why La Roche-Posay Anthelios products have some of the highest UVA star ratings according to the Boots Star Rating method.

◈

Photostability — protection does not weaken in the sun

Terephthalylidene Dicamphor Sulfonic Acid is photochemically stable: it does not decompose under UV radiation, maintaining effectiveness throughout sun exposure. In comparison: avobenzone (BMDM) is photounstable, requiring stabilizers like octocrylene or Tinosorb. Mexoryl SX is one of the few UVA filters that does not require additional photostabilization.

✧

Water solubility — ideal for lightweight formulations

Unlike most UVA filters (oil-soluble), Mexoryl SX dissolves in water → easily incorporated into the aqueous phase without the need for large amounts of oily components. Allows for the creation of lightweight, invisible fluids and essences with effective UVA protection. Often combined with oil-soluble Mexoryl XL (drometrizole trisiloxane) for complete UVA+UVB coverage.

Suitable for

Daily UVA protectionAnti-aging photoprotectionLightweight SPF formulations

Main Actions

✓ Broad-spectrum UVA filter (290–400 nm)✓ Protection against UVA-I✓ Photostable

Mexoryl SX + Mexoryl XL — Anthelios system

La Roche-Posay Anthelios is based on a combination: Mexoryl SX (water-soluble, UVA) + Mexoryl XL (drometrizole trisiloxane, oil-soluble, UVA+UVB) + other filters. Together they provide full spectrum coverage of 290–400 nm. This system is protected by L'Oréal patents — that is why Mexoryl is rarely found outside of L'Oréal Group products.

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