Healthy skin provides a barrier between the inside of the body and
the outside environment. A rash means some change has affected the skin.
Rashes are generally caused by skin irritation, which can have many
causes. A rash is generally a minor problem that may go away with home
treatment. In some cases a rash does not go away or the skin may become so
irritated that medical care is needed.
In adults and older
children, rashes are often caused by contact with a substance that irritates
the skin (contact dermatitis). The rash usually starts within 48
hours after contact with the irritating substance. Contact dermatitis may cause
mild redness of the skin or a rash of small red bumps. A more severe reaction
may cause swelling, redness, and larger blisters. The location of the rash may
give you a clue about the cause.
Contact dermatitis does not always
occur the first time you are in contact with the irritating substance (allergen). After you have had a reaction to the
substance, a rash can occur in response to even very small amounts of the
substance. Contact dermatitis is not serious, but it is often very itchy.
Common causes of contact dermatitis include:
- Poisonous plants, such as
poison ivy, oak, or sumac.
detergents, shampoos, perfumes, cosmetics, or lotions.
- Jewelry or
- New tools, toys, appliances, or other
Latex. Allergy to natural rubber latex affects people
who are exposed to rubber products on a regular basis, especially health care
workers, rubber industry workers, and people who have had multiple surgeries.
Latex allergies can cause a severe reaction.
Rashes may occur with viral infections, such as
herpes zoster; fungal infections, such as a yeast
infection (Candida albicans); bacterial infections, such
sexually transmitted infections (STIs). Rashes may also
occur as a symptom of a more serious disease, such as liver disease, kidney
disease, or some types of cancer.
Rashes may also appear
after exposure to an insect or a parasite, such as the
scabies mite. You may develop a rash when you travel
to a rural area or go hiking or camping in the woods.
A rash may
be a sign of a chronic skin problem, such as
seborrheic dermatitis. Other causes of rash include
dry, cold weather; extremely hot weather (heat rash); and emotional stress.
Emotions such as frustration or embarrassment may lead to an itchy rash.
Some medicines can cause a rash as a side effect. A very
rare and serious type of generalized red rash called toxic epidermal necrolysis
(TEN) may occur after using sulfa drugs. TEN can cause the skin to peel away, leaving large areas of tissue
that weep or ooze fluid like a severe burn. TEN may occur after the use of some
medicines. If this type of rash occurs, you
need to see a doctor.
The need for medical treatment often depends on what other
symptoms are present. A rash that occurs with other symptoms, such as shortness
of breath or fever, may mean another problem, such as a serious
allergic reaction or infection.
Check your symptoms to decide if and when you should see a doctor.