Terephthalylidene Dicamphor Sulfonic Acid is a highly photostable, water-soluble organic UV filter that provides broad-spectrum protection primarily against UVA rays. Patented under the trade name Mexoryl SX, it is a cornerstone in modern suncare for preventing photoaging and DNA damage by absorbing solar radiation in the 290–400 nm range, with a peak absorbance at 344 nm.
- INCI Name:
- Terephthalylidene Dicamphor Sulfonic Acid
- Chemical/Scientific Name:
- 3,3′-(1,4-phenylenedimethylidyne)bis[7,7-dimethyl-2-oxobicyclo[2.2.1]heptane-1-methanesulfonic acid]
- Common Aliases:
- Ecamsule, Mexoryl SX
| Category: | Sun Protection |
| Source Origin: | Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Cosmetics, Personal Care, Dermatology |
| Solubility: | Water-soluble |
At a Glance: Properties & Effects
| Sun Protection: | |
| Formula Stability: | |
| Irritation Risk: |
- Primary Benefits:
- Provides excellent protection against UVA radiation (UVA II and some UVA I), reducing the risk of long-term skin aging.
- Exhibits exceptional photostability, meaning it does not degrade significantly upon exposure to sunlight.
- Enhances the overall efficacy of sunscreen formulations by working synergistically with oil-soluble filters.
- Potential Risks:
- Extremely low risk of contact dermatitis or photoallergy compared to older chemical filters.
- Limited availability in some regions due to specific local regulatory monograph status.
Biological Action & Cosmetic Profile
Ecamsule functions by absorbing the energy of UV photons. When UV radiation strikes the molecule, electrons transition to an excited state; as they return to a ground state, the energy is dissipated as harmless heat. Unlike many other organic filters, this molecule remains structurally intact during this process, allowing it to maintain its protective capacity over prolonged sun exposure. Its peak absorption at 344 nm makes it particularly effective at bridging the gap between short-wave UVB and long-wave UVA radiation.
Because the molecule is water-soluble, it resides in the aqueous phase of an emulsion. Most other UV filters, such as Avobenzone or Octocrylene, are oil-soluble. Distributing filters across both phases creates a more uniform, continuous protective film on the skin’s irregular surface. This dual-phase approach minimizes “gaps” in coverage that occur when a formula relies solely on one phase, significantly boosting the SPF and PA ratings of the finished product.
The acidic nature of the sulfonic acid groups requires neutralization during the formulation process, typically with bases like Triethanolamine or Tromethamine. Once neutralized, the resulting salt is highly stable and compatible with a wide variety of cosmetic ingredients. It does not penetrate the skin deeply, remaining primarily in the stratum corneum, which further enhances its safety profile and reduces the likelihood of systemic absorption.
Broader Applications & Origins
Initially developed and patented by L’Oréal in the 1980s, this ingredient revolutionized suncare by addressing the instability issues prevalent in UVA protection at the time. While most sunscreens focused on UVB (burning), the introduction of Ecamsule allowed for reliable, long-wear protection against UVA (aging). It is now used globally in sunscreens, daily moisturizers, and anti-aging creams where broad-spectrum integrity is a priority.
Routine Integration
- Synergies:
- Avobenzone: Ecamsule helps stabilize this filter, which is notoriously prone to degradation, leading to superior UVA protection.
- Titanium Dioxide: Combining organic and inorganic filters broadens the total spectrum of protection.
- Glycerin: Often paired in water-based formulations to maintain skin hydration without compromising the UV film.
- Tocopherol: Antioxidants provide a second line of defense against free radicals that bypass UV filters.
Clinical Consensus & Safety
Extensive evaluations by the Scientific Committee on Consumer Safety (SCCS) and the Cosmetic Ingredient Review (CIR) Expert Panel have concluded that Terephthalylidene Dicamphor Sulfonic Acid is safe for use in cosmetics at concentrations up to 10% (expressed as the free acid). Clinical studies demonstrate that it has a negligible potential for skin irritation or sensitization. Furthermore, human environmental impact studies suggest it is less harmful to aquatic ecosystems than many other common chemical filters, such as oxybenzone.
Is this ingredient safe for sensitive skin?
Yes, Ecamsule is specifically favored in dermatological sunscreens designed for sensitive or reactive skin due to its low irritation profile and lack of significant skin penetration.
Does it protect against both UVA and UVB?
While it provides some UVB coverage, its primary strength is in the UVA spectrum (specifically UVA II). It is almost always paired with UVB filters like Ethylhexyl Triazone to ensure full-spectrum protection.
Why is it often called Mexoryl SX?
Mexoryl SX is the trade name used by the manufacturer (L’Oréal). Most consumers recognize the name from the labeling of brands like La Roche-Posay and Vichy, but the INCI name remains Terephthalylidene Dicamphor Sulfonic Acid.