Ringworm - Most of these infections are caused by a group of keratinophilic moulds known collectively asdermatophytes. They cause a complex of diseases, collectively known as ringworm (clinical name Tinea), which affects the keratin in hair, nails and stratumcorneum (top layer) of theskin. About 20 species of dermatophyte fungi from the genera Trichophyton, Microsporumand Epidermo-phytonare responsible. Most infections are caused by asingle species, Trichophytonrubrum.

Ringworms also occur in animals and these may spread to humans; transfer is commonest with Microsporum canis, the cause of ringworm in cats and dogs. Ringworm lesions vary considerably in appearance, according to the site of the infection and the species of fungus involved. Sometimes there is only dry scaling orhyperkeratosis, but more commonly there is irritation, inflammation, swelling and vesicles. More inflammatory lesions with weeping vesicles, pustules and ulceration areusually caused by animal ringworm.

The spreading, ring-like lesions with a raised, inflammatory border from which the disease name derives are seen on the body, face and scalp. In infections of the scalp there is scaling and hair loss and sometimes a severe inflammatory response resulting in a raised boggy lesion called a kerion ­ this needs to be diagnosed and treated promptly otherwise there may be permanent hair loss. In nail infection, the nail becomes discoloured, thickened, raised and crumbly. Ringworm is the only truly contagious fungal infection and spreads through direct or indirect contact with an infected individual or animal.