Pistacia Lentiscus Gum
Mustic gum is an aromatic resin coming from the bark of a tree that grows on the Greek island of Chios. It was traditionally used as a chewing gum to clean the teeth and freshen the breath thanks to its anti-microbial properties.
As for modern skincare, it is the active ingredient in a skin care complex trade named PoreAway, that is claimed to tighten dilated pores and reduce shine. It works by blocking 5α reductase type I, an enzyme that has an important role in the sebum-producing process (by converting testosterone to dihydrotestosterone, aka DHT, that is the main sebum producing hormone in the skin).
Do not expect miracles though: according to the in-vivo test conducted by the manufacturer, 2% PoreAway refined pores only by 8% after 14 days and 15% after 28 days. We are not sure if this is a change that you can really feel and see on your skin, or if it's just a "statistically significant change" that can be measured in the lab.