Rashes

A rash is often due to 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, 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, patches over joints and along the scalp. It is sometimes itchy. Fingernails may also be affected.
Impetigo — Common in children, this infection is from bacteria that live in the top layers of the skin. It appears as red sores that turn into blisters, ooze, then form a honey colored crust over all or part of the rash.
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. It usually affects only one side of the body.
Childhood illnesses such as chickenpox, measles, roseola, rubella, hand-foot-mouth disease, fifth disease, and scarlet fever.
Medicines
Insect bites or stings.
Many medical conditions can cause a rash as well. These include:

• Lupus erythematosus (an immune system disease)
  Rheumatoid arthritis, especially the juvenile type
• Kawasaki disease (inflammation of the blood vessels)
  Certain body-wide (systemic) viral, bacterial or fungal infections