Causes of a Full Body Rash

The skin plays a critical role in protecting the body, and provides important clues to overall health. A skin rash, for instance, may simply indicate the skin is irritated -- or may signal a more serious health problem. While localized rashes, or those that develop on small areas of the body, are usually a reaction to an skin irritant, allergy or related to a skin condition, widespread rashes often spread via the blood and tend to be more serious. These full body rashes are typically caused by an infection, severe allergy or drug reaction.

Infections

Widespread rashes that appear as small, pink spots on the chest, back and stomach may be connected to a viral illness. Most common in children, other typical signs include fever, cold symptoms or diarrhea. Viral rashes tend to disappear after a few days, as the infection resolves. Other infections that can lead to widespread rashes include chicken pox, measles, scarlet fever, fifth disease, and roseola.

Allergies

An allergic response to a drug or food can cause hives, which appears as a skin rash. Topical, oral or injected drugs have the potential to trigger allergies, which can range from mild to severe, life-threatening situations. When the allergic response is spread by the blood, the rash can occur on the skin all over the body. Skin rashes may also be related to allergic contact dermatitis, caused by skin contact with allergens such as nickel, topical antibiotics, latex or the chemicals in cosmetics, shampoos or perfume.

Drug Reactions

Full body rashes may also be caused by a nonallergic side effect of medications. For example, corticosteriods can cause an acne-like rash, blood thinners can lead to tiny bruises which may appear as a widespread rash, and some antibiotics cause a rash by making the skin extra sensitive to sunlight. Rarely, drugs can lead to skin rashes that accompany life-threatening medication reactions. If you experience a rash after starting any drug, contact your doctor immediately.

Other Causes

There are numerous causes of skin rash, and some rashes that typically affect small areas can become widespread. Dermatitis, an inflammation of the skin which leads to dry, itchy or red skin, sometimes spreads and appears as a full body rash. Psoriasis, characterized by a scaly rash, can also extend to most areas of the body. Heat rash, hot tub rash, poison ivy or poison oak may also become a generalized rash, depending on the extent of skin exposure. Infrequently, a widespread rash can be a sign of a serious medical condition.

Warnings

Rashes can be red, itchy, dry or scaly, and they can appear as blotches, welts or blisters. They sometimes disappear on their own, or when the cause is removed. Do not treat full-body rashes on your own, as the cause of these rashes should be evaluated by a doctor or dermatologist. If you have a rash that covers the body, or a rash that is painful, blistering, or looks infected, see a doctor right away. Seek urgent medical attention, or call 911, if you have a fever with a full-body rash, if the rash is spreading quickly, or if breathing becomes difficult.

Reviewed by Kay Peck, MPH RD