Chemical UVB sunscreen/sunblock: phenylbenzimidazole sulfonic acid (ensulizole)

Generic name: phenylbenzimidazole sulfonic acid (ensulizole)

Brand(s): Various

Type: Chemical

Range of UV spectrum covered: UVB, part of UVA (UVA-2)

Wavelengths covered: 290-340 nm

Stability:
Ensulizole does not seem to undergo much degradation when exposed to sunlight. It may also partly protect other UV blockers, such as avobenzone, from such degradation. However, the data on the stability of ensulizole is somewhat limited.

Summary:
Ensulizole is a chemical sunscreen agent that absorbs primarily UVB radiation. It provides some protection against short UVA (a.k.a. UVA-2) but not long UVA (UVA-1) and cannot be considered a comprehensive UVA blocker. In salt form, it is water soluble and often used in light, low-oil/non-greasy formulations. Ensulizole appears to have a reasonably good safety profile.

Details:
Ensulizole is a chemical sunscreen agent that absorbs primarily UVB radiation. It provides some protection against short UVA (a.k.a. UVA-2) but not long UVA (UVA-1) and cannot be considered a comprehensive UVA blocker UVA.

If in the form of free acid, ensulizole (phenylbenzimidazole sulfonic acid) is somewhat soluble in oil but poorly soluble in water. However, its salts, which are similarly effective as UV blockers, are soluble in water and tend to feel lighter on the skin. This property made ensulizole (in salt form) a common ingredient in sunscreen lotions and moisturizers whose esthetic goal is a non-greasy finish.

Ensulizole does not seem to undergo much degradation when exposed to sunlight. It may also partly protect other UV blockers, such as avobenzone, from such degradation. However, the data on the stability of ensulizole stability is somewhat limited. Ensulizole appears to have a reasonably good safety profile with low risk of irritation. Rare cases of dermatitis induced by ensulizole have been reported.