Diethylhexyl Syringylidenemalonate

Diethylhexyl Syringylidenemalonate (DESM) is a photostabilizer, antioxidant, and SPF booster.

One of DESM's main roles is stabilizing UV filters, especially avobenzone. Avobenzone is notoriously unstable when exposed to sunlight. By enhancing the stability of these filters, DESM helps maintain the sunscreen's effectivess through wear. It also helps improve protection against long-wave UVA rays by increasing the wavelength of the formula.

Besides enhancing UVA protection, DESM can boost the SPF of high-SPF formulations by up to 5 units.

DESM also preserves the color integrity of cosmetic products and helps reduce the chance of yellowing of fading due to light exposure.

This ingredient is typically found in concentrations between 0.3% - 0.5%. There are currently no maximum usage limits by regulatory bodies.

Though this ingredient is a chemical UV filter, it can often be found in "100% mineral" sunscreens. This is due to regulatory loopholes.