Superficial fungi are capable of germinating on the dead outer horny layer of skin by producing enzymes (keratinases) that allow them to digest keratin, resulting in an accumulation of epidermal scale and an inflammatory response. Cutaneous fungal infections are named for the location on the body and include tinea pedis, tinea cruris, tinea capitis (discussed in Chapter 9: Hair and Nail Disorders), tinea corporis, and tinea unguium (onychomycosis). Yeast infections such as cutaneous candidiasis and tinea versicolor are also discussed in this chapter. (N.B.Despite having “tinea” in its name, tinea versicolor is actually a yeast.)

Fungal infections may be acquired by person-to-person contact, animal contact, especially with kittens and puppies, as well as contact with inanimate objects such as shared towels and contaminated exercise machines. Additional risk factors include a family history of tinea infections, a lowered immune status as seen in patients with acquired immunodeficiency syndrome (HIV/AIDS), diabetes, collagen vascular diseases, or those on long-term systemic steroid therapy. Infections typically occur in the warm, moist, occluded cutaneous environments found in the groin, axillae, and feet.