Rash (cont.)

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How are common skin rashes diagnosed?

The term rash has no precise meaning but often is used to refer to a wide variety of skin disorders. In normal conversation, a rash is any inflammatory condition of the skin. Dermatologists have developed various terms to describe skin rashes. The first requirement is to identify a primary, most frequent feature. Then, other characteristics of the rash are noted including density, color, size, consistency, tenderness, shape, and perhaps temperature. The configuration of the rash is described using adjectives such as "circular," "ring-shaped," "linear," and "snake-like."

Finally, the distribution of the rash on the body can be very useful in diagnosis since many skin diseases have a predilection to appear in certain body areas. Although certain findings may be a very dramatic component of the skin disorder, they may be of limited value in producing an accurate diagnosis. These include findings such as ulcers, scaling, and scabbing. Using this framework, it is often possible to develop a small listing of the possible diseases to be considered. Below is a short discussion of some common categories of skin rashes:

  • Noninfectious, common rashes localized to a particular anatomical areas

  • Rashes produced by fungal or bacterial infection

  • Widely distributed rashes affecting large portions of the skin

Although most rashes are seldom signs of immediate impending doom, self-diagnosis is not usually a good idea. Rashes that quickly resolve are generally not dangerous. Proper evaluation of a skin rash requires a visit to a doctor or other health-care professional.

Scaly patches of skin produced by fungal or bacterial infection

When infections appear as rashes, the most common culprits are fungal or bacterial infections.

Fungal infections: Fungal infections are fairly common but don't appear nearly as often as rashes in the eczema category. Perhaps the most common diagnostic mistake made by both patients and non-dermatology physicians is to almost automatically call scaly rashes "a fungus." For instance, someone with several scaly spots on the arms, legs, or torso is much more likely to have a form of eczema or dermatitis than actual ringworm (the layman's term for fungus). Likewise, yeasts are botanically related to fungi and can cause skin rashes. These tend to affect folds of skin (like the skin under the breasts or the groin). They look fiery red and have pustules around the edges. As is the case with ringworm, many rashes that are no more than eczema or irritation get labeled "yeast infections."

Fungus and yeast infections have little to do with hygiene -- clean people get them, too. Despite their reputation, fungal rashes are not commonly caught from dogs or other animals, nor are they easily transmitted in gyms, showers, pools, or locker rooms. In most cases, they are not highly contagious between people either.

Treatment is usually straightforward. Many effective antifungal creams can be bought at the drugstore without a prescription, including 1% clotrimazole (Lotrimin, Mycelex) and 1% terbinafine (Lamisil). In extensive cases, or when toenails are involved, oral terbinafine may be useful.

If a fungus has been repeatedly treated without success, it is worthwhile considering the possibility that it was never really a fungus to begin with but rather a form of eczema that should be treated entirely differently. A fungal infection can be independently confirmed by performing a variety of simple tests.

Bacterial infections: The most common bacterial infection of the skin is impetigo. Impetigo is caused by staph or strep germs and is much more common in children than adults. Eruptions caused by bacteria are often pustular (the bumps are topped by pus) or may be plaque-like and quite painful (cellulitis). Again, poor hygiene plays little or no role. Nonprescription antibacterial creams like bacitracin (Neosporin) are not very effective. Oral antibiotics or prescription-strength creams like mupirocin (Bactroban) are usually needed.

Medically Reviewed by a Doctor on 2/7/2013

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