Mastic is the dried resin of Pistacia lentiscus, a shrub cultivated almost exclusively on the Greek island of Chios, where it has been harvested for over two thousand years. The resin — collected as “tears” that weep from cuts in the bark — has EU protected-designation-of-origin status, a rarity for a cosmetic ingredient.
How it works
The resin is rich in triterpenic acids, chiefly masticadienonic and isomasticadienonic acid. In cosmetic research these have been studied for their effect on sebum: published work has associated topical mastic with reduced sebum output and a measurable reduction in the appearance of pore size over several weeks of use.
One proposed mechanism runs through 5α-reductase, the enzyme that converts testosterone to the more potent dihydrotestosterone within the sebaceous gland — the same pathway targeted by several oral acne and hair-loss medicines, here acting only at the skin surface. Mastic’s triterpenes have shown inhibitory activity against this enzyme in laboratory studies.
The resin also has well-documented antimicrobial activity — historically it was chewed as a breath-freshening gum, which is where the word “masticate” comes from.
In formulation
Used in mattifying and pore-refining products for combination and oily skin, typically as the film-forming refining agent in oil-free gel textures. The effect on pore appearance builds with continued use and reverses when use stops — pore size itself is genetically determined.
Tolerance is good; it is neither exfoliating nor photosensitising.
