A simple rash is called dermatitis, meaning inflammation of the skin. Contact dermatitis is caused by things your skin touches, such as:

• Chemicals in elastic, latex, and rubber products
• Cosmetics, soaps, and detergents
• Dyes and other chemicals in clothing
• Poison ivy, oak, or sumac

Seborrheic dermatitis is a rash that appears in patches of redness and scaling around the eyebrows, eyelids, mouth, nose, the trunk, and behind the ears. If it happens on your scalp, it is called dandruff in adults and cradle cap in infants.

Age, stress, fatigue, weather extremes, oily skin, infrequent shampooing, and alcohol-based lotions aggravate this harmless but bothersome condition.

Other common causes of a rash include:

• Eczema (atopic dermatitis) -- tends to happen in people with allergies or asthma. The rash is generally red, itchy, and scaly.
• Psoriasis -- tends to occur as red, scaly, itchy patches over joints and along the scalp. Fingernails may be affected.
• Impetigo -- common in children, this infection is from bacteria that live in the top layers of the skin. Appears as red sores that turn into blisters, ooze, then crust over.
• Shingles -- a painful blistered skin condition caused by the same virus as chickenpox. The virus can lie dormant in your body for many years and re-emerge as shingles.
• Childhood illnesses such as chicken pox, measles, roseola, rubella, hand-foot-mouth disease, fifth disease, and scarlet fever.
• Medications and insect bites or stings.

Many medical conditions can cause a rash as well. For example:

• Lupus erythematosus
• Rheumatoid arthritis, especially the juvenile type
• Kawasaki disease

Most simple rashes will improve with gentle skin care and avoiding irritating substances. Follow these general guidelines:

• Avoid scrubbing your skin.
• Use as little soap as possible. Use gentle cleansers instead.
• Avoid applying cosmetic lotions or ointments directly on the rash.
• Use warm (not hot) water for cleaning. Pat dry, don't rub.
• Eliminate any newly added cosmetics or lotions.
• Leave the affected area exposed to the air as much as possible.
• Try calamine medicated lotion for poison ivy, oak, or sumac as well as other types of contact dermatitis.

Hydrocortisone cream (1%) is available without a prescription and may soothe many rashes. If you have eczema, apply moisturizers over your skin. Try oatmeal bath products, available at drugstores, to relieve symptoms of eczema, psoriasis, or shingles.

For psoriasis, you may need a prescription. You could also talk to your doctor about ultraviolet (UV) light therapy. It is safest to have such treatment under medical supervision. However, not all clinics or hospitals offer light therapy. Home units are available, but the cost is not always covered by insurance. If you do purchase a home unit, look for a device that delivers narrow band UVB light.

For seborrheic dermatitis, try applying small amounts of anti-dandruff shampoo to patches of this scaly rash on your skin, especially near hairy areas like your eyebrows. Leave on for 10 minutes and then carefully rinse off. If the shampoo feels irritating or your skin becomes redder, STOP use.

For impetigo, an antibacterial cream or oral antibiotic is generally prescribed.

See article on poison ivy, oak, and sumac to learn how to treat and prevent this type of contact dermatitis.

Call 911 if:

• You are short of breath, your throat is tight, or your face is swollen
• Your child has a purple rash that looks like a bruise

Call your health care provider if:

• You have joint pain, fever, or a sore throat
• You have streaks of redness, swelling, or very tender areas as these may indicate an infection
• You are taking a new medication -- DO NOT change or stop any of your medications without talking to your doctor
• You may have a tick bite
• Home treatment doesn't work, or your symptoms get worse

Your doctor will perform a physical examination. He or she will ask questions about your medical conditions, medications, health problems that run in your family, and recent illnesses or exposures. Questions may include:

• When did the rash begin?
• What parts of your body are affected?
• Does anything make the rash better? Worse?
• Have you used any new soaps, detergents, lotions, or cosmetics recently?
• Have you been in any wooded areas recently?
• Have you had any change in your medications?
• Have you noticed a tick or insect bite?
• Have you eaten anything unusual of late?
• Do you have any other symptoms like itching or scaling?
• What are your underlying medical problems? Do you have, for example, asthma or allergies?

Tests may include:

• Allergy testing
• Blood tests
• Skin biopsy
• Skin scrapings

Depending on the cause of your rash, treatments may include medicated creams or lotions, medications taken by mouth, or skin surgery.

Many primary care doctors are comfortable dealing with common rashes, but for more complicated skin disorders, a referral to a dermatologist may be necessary.

• Identify and then stay away from products that irritate your skin. If allergies are suspected, your doctor may want to consider skin testing.
• Receive appropriate vaccines for childhood illnesses, like the varicella vaccine for chicken pox and MMR immunization (a combination vaccine that protects against measles, mumps, and rubella).
• Get strep throat treated right away to prevent scarlet fever.
• Wash your hands frequently to prevent spreading viruses like roseola, hand-foot-mouth disease, and fifth disease.
• Learn relaxation methods like yoga, meditation, or tai chi. Stress aggravates many rashes, including eczema, psoriasis, and seborrheic dermatitis.

Auerback PS, ed. Wilderness Medicine. St. Louis, Mo: Mosby; 2001.

Marx J. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002.