What is a rash?

Causes and Symptoms

Rashes may have many different causes: infection, inflammation, irritation, an allergic reaction, and systemic disease. Rashes usually vary in color from pale pink to red. They take many different forms: flat, raised, puffy, scaly, blistery, or crusted. They may be pruritic. Rashes may involve a small portion of the skin or cover much of the body. They may come in characteristic shapes, such as a bull’s-eye, or may appear irregular. A rash may be accompanied by other signs and symptoms that help the health care provider determine the cause of the rash, or a rash may form part of a constellation of signs and symptoms diagnostic of another disease or disorder.

Infectious rashes may be caused by bacteria, viruses, or fungi. For example, impetigo is caused by either staphylococcal or streptococcal bacteria, cold sores are caused by a herpesvirus, and athlete’s foot is caused by a fungus. Some infectious rashes are highly contagious among children or family members and others.

Rashes associated with inflammation include allergic responses to drugs, certain foods, stings, and poison ivy. Allergic rashes are typically red and itchy. They may be flat or may arise as wheals. Many allergic rashes are merely annoying, but some can be part of a life-threatening condition called anaphylaxis. Symptoms of anaphylaxis include blockage of the airways, a rash, and cardiac problems. Children can go into anaphylactic shock after eating a food to which they are highly allergic (such as shellfish, peanuts, or strawberries) or after being stung by a bee.

A common, but not usually serious, rash in infants is heat rash, or miliaria rubra. It is also called “prickly heat.” This rash is most common in hot and humid environments and on areas of the body covered by tight clothing.

Many of the so-called childhood diseases are characterized by fever and rash: measles, rubella (German measles), chickenpox, and fifth disease. The rash associated with each of these has distinctive features that help in the diagnosis of the disease. For example, the child with fifth disease has bright red cheeks, the so-called “slapped cheek” phenomenon, and a fine lacy rash on the trunk and extremities. The rash of rubella begins on the face and spreads rapidly to the trunk, arms, and legs. All these childhood diseases are related to systemic viral infections. Scarlet fever, on the other hand, is a streptococcal infection accompanied by a rash. Again, the characteristics of the rash help in making the diagnosis: It has a fine sandpaper-like feeling when touched.

Treatment and Therapy

The treatment of rashes depends on the cause. A common rule of thumb is that if a rash is wet, the treatment is to dry it, and vice versa. For example, an oozing rash such as that caused by poison ivy may be relieved by a drying paste that relieves itching, while a dry rash may be best treated with an ointment or by an oatmeal bath.

Some rashes will resolve on their own, and the main job of parents and health care providers is to relieve a child’s unpleasant symptoms, such as itching, that go along with the rash. Patients with rashes that itch need to receive medications to relieve itching, such as antihistamines, so that they will not complicate their condition by scratching the affected skin. Most antihistamines, however, cause the side effect of sleepiness. Soothing oatmeal baths or moisturizing lotions can relieve itching without causing sleepiness.

Treatments for rashes can be either topical or systemic. Topical treatments are put directly on the skin. For example, athlete’s foot is treated with topical ointment or powder containing an agent that will kill the fungus that causes the condition. Impetigo, on the other hand, is usually treated with systemic antibiotics to kill the causative bacteria.

A mainstay of dermatological treatment is steroid medications. Topical steroids such as hydrocortisone cream or ointment are applied directly to the skin and may be covered with a dressing. In some cases, as in a serious case of poison ivy, steroids may be given orally or by injection. Steroids have potential serious adverse effects, so most health care providers use them sparingly. They should almost never be used on the face or eyelids unless so prescribed by a physician.

Perspective and Prospects

Rashes are an extremely common problem in childhood and adolescence. Parents can often diagnose rashes themselves and treat them with appropriate over-the-counter products. Rashes that are associated with other symptoms, whose origin is unclear, or that fail to clear up in a reasonable amount of time should be evaluated and treated by a qualified health care provider.

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