Humulene (also known as α-caryophyllene, α-Humulene) is a ring-opened isomer of β-caryophyllene, with powerful anti-inflammatory activity equal to dexamethasone in an animal model. α-Humulene has been found in many aromatic plants on all continents, often together with its isomer β-caryophyllene. Proven α-humulene emitters into the atmosphere are pine trees, orange orchards, marsh elders, tobacco, and sunflower fields. Humulene possesses both topical and systemic anti-inflammatory properties and is an effective analgesic when taken topically, orally, or by aerosol. Humulene can produce ROS, leading to an antineoplastic effect by inducing apoptosis; although at moderate levels, ROS can increase tumor growth. β-Caryophyllene was synergistic with humulene in one study. Interestingly, humulene was shown to increase secretion of IL-8, a chemokine with various functions, including promoting angiogenesis, helpful in wound healing but not typically associated with anticancer compounds.