Rash

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Overview

A rash is an area of inflamed and irritated skin. Rashes are characterized by redness, itching, swelling, and various types of skin lesions (e.g., macules, papules, nodules, plaques, pustules, vesicles, wheals). In some cases, the area of skin affected is dry and sensitive, cracks or flakes, and is warm to the touch.

Most people experience some type of itchy skin rash during their lifetime. In most cases, simple rashes are not serious; but rarely, a rash can indicate a life-threatening condition. It is important to see a physician for the correct diagnosis of any rash.

Types
There are many different types of skin rashes. Dermatitis, also called eczema, is a common rash characterized by inflammation, redness, swelling, and itching. In some cases, blistering and oozing (weeping) also occur. The most common form of eczema is called atopic dermatitis. Other forms include contact dermatitis, seborrheic dermatitis, and nummular dermatitis.

Atopic dermatitis affects 10–15% of children and causes rashes and itching, which may be severe. This condition usually improves later in childhood, but many people are affected to some degree throughout their lives. Genetics play an important role in the occurrence of atopic dermatitis and families with a history of asthma and allergies experience a higher incidence rate.

Contact dermatitis results from exposure to an irritating substance, such as detergents, soaps, certain plants, and solvents. It can also result from an acquired hypersensitivity to a substance that causes an allergic reaction (allergen). In this case, the first exposure to a particular allergen does not trigger a reaction or irritation, but causes the person to develop sensitivity. Subsequent exposure then produces an itchy rash.

Allergenic substances include poison ivy, poison oak, and poison sumac; nickel plating on jewelry; and rubber or glues in shoes. Some allergens (e.g., sunscreens, fragrances) may become sensitizing only when exposed to the sun.

Seborrheic dermatitis often occurs on the face, behind the ears, or on the scalp (called dandruff). Waxy scales and reddened skin areas characterize the condition. Nummular dermatitis can develop at any age, but is most common after the age of 60. It is a long-lasting (chronic) condition characterized by round plaques of eczema.

Rashes occur frequently in infants and young children. Diaper rash (diaper dermatitis) is the most common skin disorder in infants and toddlers. The most common cause for diaper rash is prolonged contact with a soiled diaper, resulting in irritation to the skin. Rubbing and chafing can worsen the rash.

Diaper rash usually responds well to frequent diaper changes and allowing the child to go without diapers for periods of time daily. Cornstarch or powder can be used as a drying agent to help reduce moisture and friction.

There are a number of other skin conditions and rashes that occur in infants. For more information about these conditions, please go to Newborn Skin. Young children are also susceptible to other types of rashes, including the following:

• Bacterial infections (e.g., impetigo, scarlet fever)
• Fungal infections (e.g., ringworm, athlete's foot)
• Heat rash (prickly heat)
• Viral infections (e.g., chickenpox, coxsackievirus, fifth disease, measles, German measles [rubella], roseola)

Pityriasis rosea is a common skin rash that develops mainly on the torso and upper extremities. The lesions are typically pink and oval with slight overlying scale, and this condition usual is not itchy. Pityriasis rosea may result from human herpesvirus 7 (HHV-7).

Hives (urticaria) is a condition characterized by the sudden eruption of elevated wheals or papules, associated with swelling and severe itching. Hives usually are caused by an allergic reaction. Treatment may include antihistamines or, in severe cases, corticosteroids.

Shingles (herpes zoster) is caused by reactivation of a dormant varicella-zoster virus (VZV), which is the same virus that causes chickenpox. Shingles usually results in a localized, unilateral (occurs on one side of the body) rash that follows a linear pattern along a nerve. Redness in the area is followed by raised bumps and blisters that become pus filled. In most cases, the lesions scab over and heal in about a week.

Risk Factors and Causes

A personal or family history of allergies or asthma increases the risk for rashes. People who spend a lot of time outdoors are at increased risk for poison ivy, poison oak, and poison sumac; and for rashes caused by insect bites.

Common causes for rashes include the following:

• Allergic reaction (e.g., resulting from an animal allergy, drug allergy, or food allergy)
• Bacterial infection (e.g., impetigo)
• Drug side effect
• Excessive skin rubbing (friction)
• Fungal infections (e.g., athlete's foot, ringworm)
• Insect bites (e.g., tick, flea, spider, mosquito)
• Parasite infection (e.g., scabies)
• Prolonged exposure to heat, moisture, or irritants (e.g., heat rash, diaper rash, contact dermatitis)

• Acne (often develops on the face, neck, back, and shoulders)
• Lupus (commonly causes a "butterfly" rash across the cheeks and under the eyes)
• Lyme disease (usually transmitted by the bite of an infected deer tick; causes a "bull's eye" rash)
• Psoriasis (typically causes round, red lesions with sharply defined edges and overlying silvery white scales [called plaques]; usually begins as small spots that progressively involve very large areas)
• Rosacea (often occurs on the forehead, nose, and chin)

Rash Resources

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