Guaiazulene

Guaiazulene, also azulon or 1,4-dimethyl-7-isopropylazulene, is a dark blue crystalline hydrocarbon and a derivative of azulene. Specifically, it is a bicyclic sesquiterpene that occurs naturally as a constituent of some essential oils, mainly oil of guaiac and chamomile oil, which also serve as its commercial sources. Various soft corals also contain guaiazulene as a principal pigment.

Guaiazulene is an FDA-approved cosmetic color additive. It is also a common component of cosmetics like shampoos or skin care products with other skin soothing compounds such as allantoin.

Guaiazulene has applications as an anti-ulcer drug, and can be also used as a volatile dye with a known evaporation rate to indicate end of use of various products (such as insecticide strips.)