Skin rash: causes, treatment and when to worry

A rash is any change in the color or texture of your skin: red patches, welts, bumps, blisters or dry, scaly skin. It can itch, burn or hurt. Most rashes are not serious and clear up with simple care or with treatment the doctor recommends.

The best clues to the cause are how it looks, where it started, when it began and whether it came with other symptoms, like a fever.

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The causes table on this page lists the usual ones. Some clues:

• Contact dermatitis: redness and itching where skin touched something, such as soaps, detergents, cosmetics, clothing dyes, latex or plants. See eczema and dermatitis.
• Eczema: red, dry, scaly, itchy skin that flares and settles.
• Hives: raised, itchy welts that move around; they can come from an allergy, a medicine or an infection.
• Shingles: pain, itching or tingling, then blisters in a stripe on one side of the body or face. See shingles.
• Impetigo: red sores that blister, ooze and form a honey-colored crust. See impetigo.
• Insect bites and reactions to a new medicine.

Dengue can cause a fever with a rash, pain behind the eyes and bone or joint pain. If you have a rash with a fever, read our dengue warning signs guide and watch closely as the fever starts to fall. If dengue is possible, the CDC advises acetaminophen and no aspirin or ibuprofen. Visitors are at risk too.

Treatment depends on the cause, and the doctor explains what fits your case. Meanwhile, if the rash is mild and you have no warning signs:

• Wash with warm, not hot, water and a gentle cleanser. Do not scrub; pat dry.
• Leave the area open to the air as much as you can.
• Avoid whatever may have set it off: a new soap, fragrance, cream or plant.
• Calamine lotion can soothe contact dermatitis, and over-the-counter hydrocortisone cream can help many rashes.
• Try not to scratch; keep nails short.
• If the doctor needs to confirm a cause, for example with blood work, she gives you a lab order for a lab near you and reviews the results with you.

If you feel pain, burning or tingling on one side of your body and then blisters appear in a stripe, get checked promptly: antiviral treatment works best when started early. If shingles is on your face or near an eye, get care the same day, because it can affect your vision.

For your safety, call 911 if you are short of breath, your throat feels tight or your face is swelling. Go to the ER for a fever with purple or bruise-like spots that do not fade when you press a glass on them, or widespread blisters with peeling skin. More in when to go to the ER.

We see children of all ages. Kids tend to get different rashes: viral rashes, hand, foot and mouth disease, chickenpox, diaper rash or impetigo. Read rashes in children.