July 12, 2011 Article on Contact Dermatitis

Contact Dermatitis Causes

There are 2 types of contact dermatitis: allergic and irritant.

• Like all allergic reactions, allergic contact dermatitis results from a reaction of the immune system.
  • The immune system overreacts to the foreign substance, usually an animal or vegetable protein. The immune system is activated to produce antibodies against this allergen. This overreaction is often called a hypersensitivity reaction.
  • The antibody, called immunoglobulin E or IgE, is stored on special cells called mast cells.
  • When they come in contact with the allergen, the antibodies promote release of chemicals and hormones called "mediators." Histamine is an example of a mediator.
  • It is the effects of the mediators that cause the symptoms of the allergic reaction, in this case an itchy rash.

• In allergic contact dermatitis, then, you have a skin reaction to something that has touched your skin at that site. Unlike most allergic reactions, the trigger is external rather than internal.
  • Your initial exposure does not cause a rash. However, it sensitizes your skin so that you will react to the next exposure. If you seem to react the first time you are exposed to an agent, you probably were exposed before without knowing.
  • Common plant allergens that cause dermatitis include poison ivy, poison oak, and poison sumac.
  • Many other substances can cause allergic reactions, including hair dyes or straighteners; the metal nickel, which is found in jewelry and belt buckles; tanning agents in leather; latex rubber; and citrus fruit, especially the peeling.
  • The fragrances in soaps, shampoos, lotions, perfumes, and cosmetics can cause a reaction.
  • Even certain medications applied to the skin can cause dermatitis.

• Irritant contact dermatitis results from coming in contact with a substance that directly damages your skin.
  • The longer the substance remains on the skin, the more severe the reaction.
  • Many chemicals, including industrial cleaning products and solvents, can cause this condition.
  • Household cleaners such as detergents can also cause dermatitis.

• People with other skin conditions, such as eczema, are most likely to develop contact dermatitis.

      

Contact Dermatitis Symptoms

Telling allergic contact dermatitis apart from irritant contact dermatitis can be very difficult. Allergic dermatitis is usually confined to the area where the trigger actually touched the skin, whereas irritant dermatitis may be more widespread on the skin.

• A red rash is the usual reaction. It appears immediately in irritant contact dermatitis, but sometimes in allergic contact dermatitis the rash does not appear for 1-2 days after the exposure.

• Your skin may blister, or you may get a raised red rash, called hives, sometimes in a pattern that points to the offending agent.

• Your skin will itch and perhaps burn. Irritant contact dermatitis tends to be more painful than itchy.

• Irritant contact dermatitis often affects the hands, which have been exposed by resting in or dipping into a container (sink, pail, tub) containing the irritant.

• Once a reaction starts, it may take as long as 4 weeks to resolve completely.

When to Seek Medical Care

If your rash does not improve or continues to spread after a couple of days of self-care, call your health care provider.

If the itching is severe and you cannot see your health care provider that day, go to a hospital emergency department.

ontact Dermatitis Treatment

In most cases, contact dermatitis does not require medical treatment.

Self-Care at Home

• Avoid touching the trigger.
• Washing with soap and cool water can remove or inactivate most of the offending substance, if it is done immediately after exposure.
• If blistering develops, cold moist compresses applied for 30 minutes 3 times a day are helpful.
• Calamine lotion and cool oatmeal baths may relieve itching.
• Oral antihistamines such asdiphenhydramine (Benadryl, Ben-Allergin) can also relieve itching.
• Do not apply antihistamine lotions to the skin, because you may have an allergic contact dermatitis from the lotion itself.
• For mild cases that cover a relatively small area, hydrocortisone cream in nonprescription strength may be sufficient

Medical Treatment

Treatment usually consists of medications to relieve the symptoms until the rash can go away on its own.

Follow-up

Avoid scratching, which worsens the inflammation.

Continue self-care until all symptoms are gone.

If you have been treated by your health care provider, complete the recommended treatment.

If you are taking oral steroid medication, finish the entire prescription, or the rash may come back. You may be taking medicine for only 3-5 days, or for as long as 4 weeks, depending on the severity of your reaction.

If you have frequent dermatitis, you may want to see an allergy specialist (allergist) to identify the cause.

Prevention

If you know what causes the dermatitis, avoid that trigger. If you cannot avoid the trigger altogether, take steps to protect your skin from the trigger.

Wearing protective clothing such as long sleeves, long pants, and gloves helps protect the skin from allergens and irritants.

Protection is especially important at an industrial site, but it is also important when working outdoors where you could come in contact with plants from the poison ivy family as well as with lawn and garden chemicals, cleaning solvents, and other toxic substances.

Take care to avoid poison ivy, poison oak, and poison sumac when enjoying the outdoors.

If you do become exposed, wash the area immediately with soap and cool water to prevent a rash from developing.

If you have dermatitis often and you do not know what is causing it, you may want to see an allergy specialist, or allergist.

• The allergist will ask you questions to try to determine what may be causing the reactions.
• If the questions do not reveal the cause, he or she may perform skin patch tests to identify the trigger.
• You can then take steps to avoid the trigger.

Authors and Editors

Author: Brian T Dillon, MD, Vice-Chief, Medical Director, Department of Emergency Medicine, Seton Northwest Hospital.

Editors: Scott H Plantz, MD, FAAEM, Research Director, Assistant Professor, Department of Emergency Medicine, Mount Sinai School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Steven L Bernstein, MD, Vice-Chair, Academic Affairs, Department of Emergency Medicine, Newark Beth Israel Medical Center; Assistant Professor, Department of Emergency Medicine, Mt Sinai School of Medicine.