These infections, also called mycoses, are common and particularly affect the skin or mucosal membranes in, for example, the mouth, anus or vagina. Fungi consist of threadlike hyphae which form tangled masses or mycelia common mould. In what is called dermatophyte (multicellular fungi) fungal infection of the hair, nails and skin, these hyphae invade the keratin. This is usually described as ‘ringworm’, although no worm is present and the infection does not necessarily occur in rings. Pityriasis versicolor and candidosis, called thrush when it occurs in the vulva, vagina and mouth, are caused by unicellular fungi which reproduce by budding and are called yeasts. Other fungi, such as actinomycosis, may cause deep systemic infection but this is uncommon, occurring mainly in patients with immunosuppressive disorders or those receiving prolonged antibiotics treatments.