Another essential oil with notable anti-influenza effects is tea tree, which is extracted from the leaves of Melaleuca alternifolia (Myrtaceae). Commercial tea tree oil is composed of terpinen-4-ol (30–48%), γ-terpinene (10–28%), α-terpinene (5–13%), 1,8-cineole (up to 15%), terpinolene (1.5–5%), p-cymene (0.5–12%), α-pinene (1–6%), and α-terpineol (1.5–8%) [30]. Tea tree oil showed 100% inhibition of influenza type A (H1N1) virus at 0.01% concentration and a median inhibitory concentration (IC50) of 6 μg/mL [31,32]. In addition, 30 min exposure of type A (H11N9) virus to tea tree oil vapor caused 100% inhibition [33]. The tea tree oil components, terpinen-4-ol, terpinolene, and α-terpineol, have shown anti-influenza virus activity against type A (H1N1), with IC50 values of 25, 12, and 250 μg/mL, respectively. α-Terpinene, γ-terpinene, and p-cymene were inactive, however [31].