July 27, 2011 Noninfectious,Common Rashes

What are noninfectious, common rashes localized to a particular anatomical area?

Common, noninfectious rashes are listed below. Since these conditions are not caused by infectious organisms, it is reasonable to attempt to treat them with over-the-counter 1% hydrocortisone cream for a week or so prior to seeking medical attention.

Seborrheic dermatitis: Seborrheic dermatitis is the single most common rash affecting adults. It produces a red, scaling eruption that characteristically affects the scalp, forehead, brows, cheeks, and external ears.

Atopic dermatitis: Atopic dermatitis, often called eczema, is a common disorder of childhood which produces red, itchy, weeping rashes on the inner aspects of the elbows and in back of the knees as well as the cheeks, neck, wrists, and ankles. It is commonly found in patients who also have asthma and hay fever.

Contact dermatitis: Contact dermatitis is a rash that is brought on either by contact with a specific chemical to which the patient is uniquely allergic or with a substance that directly irritates the skin. Some chemicals are both irritants and allergens. This rash is also occasionally weepy and oozy and affects the parts of the skin which have come in direct contact with the offending substance. Common examples of contact dermatitis caused by allergy are poison ivy or poison oak (same chemical, different plant) and reactions to costume jewelry containing nickel.

Diaper rash: This is a common type of contact dermatitis that occurs in most infants who wear diapers when feces and urine are in contact with skin for too long.

Stasis dermatitis: This is a weepy, oozy dermatitis that occurs on the lower legs of individual who have chronic swelling because of poor circulation in veins.

Psoriasis: This bumpy scaling eruption never weeps or oozes and tends to occur on the scalp, elbows, and knees. It leads to silvery flakes of skin that scale and fall off.

Nummular eczema: This is a weepy, oozy dermatitis that tends to occur a coin-shaped plaques in the winter time and is associated with very dry skin.

Next: How are common skin rashes diagnosed?

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 actualringworm (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 isimpetigo. 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.

Widely distributed rashes affecting large portions of the skin

Outbreaks of this sort are usually either viral or allergic.

Viral rash: While viral infections of the skin itself, like herpes or shingles (a cousin ofchickenpox), are mostly localized to one part of the body, viral rashes are more often symmetrical and everywhere. Patients with such rashes may or may not have other viral symptoms like coughing, sneezing, or stomach upset (nausea). Viral rashes usually last a few days to a week and go way on their own. Treatment is directed at relief of itch, if there is any.

Other rashes

Hives or "welts" (urticaria) are itchy, red bumps that come and go rapidly over six to eight hours on various parts of the body. Most hives run their course and disappear as mysteriously as they came. Heat rash is a skin irritation caused by excessive sweatingduring hot, humid weather. It can occur at any age but is most common in young children. Heat rash looks like a red cluster of pimples or small blisters. It is more likely to occur on the neck and upper chest, in the groin, under the breasts, and in elbow creases.

What is the treatment for a rash?

Most rashes are not dangerous to a person or people in the vicinity (unless they are part of an infectious disease such as chickenpox). Many rashes last a while and get better on their own. It is therefore not unreasonable to treat symptoms like itchy and/or dry skin for a few days to see whether the condition gets milder and goes away.

Nonprescription (over-the-counter) remedies include

• anti-itch creams containing camphor, menthol, pramoxine (Itch-X, Sarna Sensitive), or diphenhydramine (Benadryl);
• antihistamines like diphenhydramine, chlorpheniramine (Chlor-Trimeton), or loratadine (Claritin, Claritin RediTabs, Alavert); andcetirizine (Zyrtec);
• moisturizing lotions.

If these measures do not help, or if the rash persists or becomes more widespread, a consultation with a general physician or dermatologist is advisable.

There are many, many other types of rashes that we have not covered in this article. So, it is especially important, if you have any questions about the cause or treatment of a rash, to contact your doctor. This article, as the title indicates, is just an introduction to common skin rashes.

A word on smallpox vaccination in patients with rashes

People with atopic dermatitis or eczema should not be vaccinated againstsmallpox, whether or not the condition is active. Patients with atopic dermatitis are more susceptible to having the virus spread on their skin, which can lead to a serious, even life-threatening condition called eczema vaccinatum. In the case of other rashes, the risk of complications is much less. Consult your doctor about the smallpox vaccine.

Rashes At A Glance

• Rash is not a specific diagnosis. It is instead a general term that means an outbreak of skin inflammation and discoloration that change the way the skin looks and feels.
• Common rashes include eczema, poison ivy, and heat rash.
• Infections that cause rashes include fungal, bacterial, or viral infection.
• Over-the-counter products to combat infection or itch may be helpful with the proper diagnosis.
• Rashes lasting more than a few days that are unexplained should be evaluated by a doctor.

Previous contributing editor:

Medical Editor: Frederick Hecht, MD

REFERENCE:

Bolognia, Jean L., Joseph L. Jorizzo, and Ronald P. Rapini. Dermatology. 2nd ed. Spain: Mosby, 2008.

Last Editorial Review: 7/6/2011