Much of the essential oils prove to be effective against the fungus, causing very common ailments such as thrush (aphthous stomatitis), ringworm and sports foot. Undoubtedly, viruses are the most insidious of all microorganisms. Unlike bacteria, they invade the cells after an invasion of the body, so identification and counteraction by the immune system are extremely difficult. Among the problems caused by viruses, we have to mention colds, flu, herpes (all its varieties), chickenpox (varicella) and measles (measles). There are few substances, natural or synthetic, that produce results in such cases, but there are also essential oils among them. The list includes cinnamon, thyme, black pepper, eucalyptus, tea bush (for some influenza and cold viruses), lavender (herpes simplex or wounds caused by cold, possibly in herpes genitalia) and geranium (for herpes zoster). Since there is solid evidence of the antivirus effect of some oils, especially with regard to flu, it should be considered whether aromatherapy could help solving the AIDS problem.