Contact Dermatitis

Picture of contact dermatitis. Contact dermatitis is a localized rash or irritation of the skin.

Dermatitis is an inflammation of the skin. Contact dermatitis is a localized rash or irritation of the skin caused by direct contact the inducing substance to which the skin reacts.

Such substances are toxic to the skin and are termed primary irritants. Others may induce an immunologic reaction called allergic contact dermatitis and include

• plant oils,
• metals,
• cleaning solutions,
• cosmetic additives,
• perfumes,
• industrial chemicals,
• topical antibiotics, and
• latex rubber additives.

There are two types of contact dermatitis: allergic and irritant. They often can appear to be visually identical.

• Allergic contact dermatitis often results from an immune response to a small, structurally simple molecule.
  • In order to become allergic to such a substance, one must have had at least one previous exposure that eventually induces an immune response.
  • This dermatitis is not caused by an antibody but is due to a cellular immune response mediated by a type of blood cell (T-lymphocytes) that has surface molecules that enable it to recognize specific chemical allergens.
  • When these lymphocytes come in contact with the allergen, they release a variety chemicals that are able to produce an itchy dermatitis.
  • Typically, this sort of reaction occurs only on the skin and requires at least 24 to 48 hours to develop.
  • Common plants that produce allergic contact dermatitis include poison ivy, poison oak, and poison sumac. The allergenic chemical is present in the oil or latex that covers stems or leaves.
  • Many other substances can cause allergic reactions, including components of hair dyes or straighteners; metallic nickel in jewelry and belt buckles; leather tanning agents; and chemical additives to latex rubber.
  • The fragrances in soaps and preservatives and emulsifiers in shampoos, lotions, perfumes, and cosmetics can cause reactions.
  • Medications applied to the skin, like neomycin (Neosporin, Neo-Fradin, Neo-Tab), are a common cause of this type of dermatitis.
• Irritant contact dermatitis results from coming in contact with a substance that is directly toxic to your skin. No allergy is required, and it will occur on the first exposure.
  • 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 (atopic dermatitis), are more likely to develop contact dermatitis.

Exposure to normal or damaged skin to irritating chemical or known allergens is a significant risk. Anyone who compulsively washes their hands many times a day can develop dermatitis induced by simple soap and water.

Common solvents used in the workplace can damage the skin, producing an irritant dermatitis and permitting allergens access to the deeper tissues. The practice of ear piercing is known to predispose to nickel allergy. The use of topical antibiotics like neomycin is associated with an allergy to this antibiotic.

Contact dermatitis is not caused by an infectious microorganism and is not contagious. Since the condition can produce open raw skin, a secondary infection can occur on the damaged skin. This secondary infection can be contagious.

Distinguishing allergic contact dermatitis from irritant contact dermatitis and other forms of dermatitis can be challenging. A full history and physical examination are frequently necessary.

• A red rash is the usual reaction. It appears immediately in irritant contact dermatitis, but in allergic contact dermatitis, the rash does not appear for one to two days after the exposure.
• Your skin may develop small fluid filled structures (vesicles) that can cause weeping, a characteristic of these sorts of eruptions. This condition is distinguished from hives (urticaria) that produce short-lived itchy welts (wheals).
• Hives are most often induced by allergic reactions to orally ingested foods and drugs, but topical contact hives occurs and is mediated by antibodies.
• Your skin will itch and perhaps burn. Irritant contact dermatitis can 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 four weeks to resolve completely.

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 an urgent care center.

Medical professionals usually diagnose contact dermatitis from your symptoms and physical examination. Blood tests and X-rays are not helpful. The evaluation of allergic contact dermatitis may require the application of chemicals to the skin for 48-72 hours (patch testing) using special occlusive dressings in an effort to reproduce the eruption.

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

• 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 one to five minutes many times a day are helpful followed by air drying, perhaps supplemented with a fan.
• Oral antihistamines such as diphenhydramine (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, over-the-counter 1% hydrocortisone cream may be sufficient.

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

• Corticosteroids, either oral or topical depending on the severity of the reaction.
  • A topical corticosteroid cream or ointment stronger than hydrocortisone may be prescribed to combat inflammation in a localized area. If the reaction covers a relatively large portion of the skin or is severe, a corticosteroid that is taken as pills or as an injection may be prescribed.
  • If the reaction covers a relatively large portion of the skin or is severe, a corticosteroid that is taken as pills or as an injection may be prescribed.
• Antihistamines: Prescription antihistamines may be given if nonprescription strengths are not adequate.

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 three to five days, or for as long as four weeks, depending on the severity of your reaction.

If you have frequent dermatitis, you may want to see a dermatologist to identify the cause.

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 a skin allergy specialist.

• You will be asked questions to try to determine what may be causing the reactions.
• If the questions do not reveal the cause, skin patch tests may be applied to identify the trigger.
• You can then take steps to avoid the trigger. There is no treatment to "cure" the allergy so the allergen must be avoided in order to prevent symptoms.

If the irritating substance causing the contact dermatitis is removed and you are not exposed to it again, your rash probably will disappear on its own in less than three weeks. Symptoms may go away sooner with treatment.

Although your rash may have resolved, your immune system will always remember the chemical to which you were allergic. So, if you encounter it at some future time your rash is likely to recur.

American Academy of Allergy, Asthma and Immunology