Bites, rashes, and itches. How to identify and treat them.

Skin rashes are commonly seen by the primary care physician. The chief cause of contact dermatitis is the plant genus Toxicodendron, but topical medications such as anesthetics, antibiotics, and preservatives also cause this condition. Commonly seen superficial fungal infections include candidiasis and several types of tinea. Microscopic identification of the organism on a potassium hydroxide (KOH) preparation establishes the definitive diagnosis. In addition to occurring in its usual sites, the herpes simplex virus can cause recurrent disease on glabrous skin areas. A positive Tzanck test establishes a diagnosis of herpesvirus infection. Mosquito, flea, and brown recluse spider bites produce diagnostic physical findings. Scabies infestation produces a distinctive eruption, and the diagnosis is made by isolating the mite or its products.