The American Academy of Dermatology defines dermatitis as an inflammation of the skin (5) generally caused by something you touch. There are two types of dermatitis: allergic contact dermatitis and irritant contact dermatitis.
Allergic dermatitis occurs minutes to hours after the allergen (the substance to which the person is allergic) touches the skin (1). The initial exposure usually does not cause a rash or any symptoms. However, it makes your skin sensitive so that you will react to the next exposure. If you react the first time you are exposed to an agent, you were probably exposed before without knowing (2).
Irritant dermatitis is caused by frequent exposure to a mild or strong irritant such as detergent or battery acid. Once the skin irritation occurs, exposure to mild substances – even water – can irritate the skin and worsen the condition (3).
Signs and symptoms
The skin reaction varies depending on the affected body part. Irritation tends to be on the eyelids, genitals and neck, and less aggressive on the soles of feet, the hands and the scalp.
Common signs and symptoms include redness, swelling, blisters, bumps, scaly skin and painful and/or itchy skin.
Common causes
There are more than 3,000 substances or allergens known to cause contact dermatitis.
According to the Centers for Disease Control and Prevention, "an estimated 50 million Americans suffer from all types of allergies (one in five Americans), including indoor/outdoor, food and drug, latex, insect, skin and eye allergies. Allergy prevalence overall has been increasing since the early 1980s across all age, sex and racial groups."
Common substances may be poison ivy, poison oak, jewelry, clothing and shoes, certain foods, some metals, cleaning products, cosmetics, perfumes and latex rubber. Even products labeled "unscented" may cause a skin reaction.
Sometimes exposure to UV light or sweat, most commonly in the presence of nickel and antibiotics, may trigger a skin reaction. For example, a person may not react to nickel unless he/she perspires or takes antibiotics and develops a rash when exposed to sunlight.
Risk factors
Certain conditions can be considered risk factors, including medical history, age, repeat exposure, occupation, gender and environment, to mention a few. Anyone can develop contact dermatitis, but having a history of lupus, psoriasis, atopic dermatitis or eczema increases the risk of developing the condition.
Occupation and environment are important factors since a person may be exposed to certain irritants or extreme weather conditions that may trigger the irritation. Hairdressers, for example, handle chemicals and are repeatedly exposed to changes in temperature.
Age is a very important factor since a younger person's immune system tends to overreact rather than the immune system of an older person (1).
Duration
The skin reaction varies in length of stay depending on the allergen or substance exposure. It may take up to four weeks to resolve completely.
If the skin is exposed frequently, the skin condition may not recover, and sometimes, it may worsen (2).
When to seek medical care
If the rash spreads rapidly to the entire body, causes difficulty breathing or causes swelling of the mouth or lips, you should seek emergency care.
If the rash seems to persist despite a couple of days of self-care or withdrawal to the irritant, call your health care provider.
How it is diagnosed
A thorough medical history and skin examination are the primary step to diagnosing it.
The American Academy of Allergy, Asthma & Immunology recommends performing an allergy testing – also known as skin, prick or blood testing – as a method for determining to what substances a person is allergic (4). The academy says skin testing is the most reliable way of testing.
A blood test is usually performed when a skin test may potentially be harmful to the patient.
How to treat it
At home, you may start by avoiding contact with the trigger and washing with soap and cool water to remove the irritant. Calamine lotion may relieve itching.
Oral histamines such as loratadine or diphenhydramine (Claritin, Benadryl) can also relieve itching and rash.
Do not apply antihistamine lotions to the skin since the lotion itself may cause a skin reaction. If you are allergic to nickel, you can cover the metal button with clear nail polish and avoid fantasy jewelry since it usually contains nickel.
Your doctor may recommend an oral medication for a bad reaction.
How to prevent it
Have your health care provider perform an allergy testing to avoid possible allergens and wear gloves that don't contain latex.
Tell your doctor if you have a reaction to any medications, substance or food since he/she may help you develop a strategy to avoid known allergens.
For more information, please visit the American Academy of Family Physicians, the American Academy of Dermatology and/or the American Academy of Allergy, Asthma & Immunology.
References:
The Lewin Group (prepared for the Society for Investigative Dermatology and the American Academy Dermatology Association). "The Burden of Skin Diseases" 2004 p. 37-40
Perryman JH, et al. "A Patch Test Study to Evaluate the Allergenicity of a Metallic Jewelry Alloy in Patients Allergic to Cobalt." Cutis. 2006 February; 77(2): 77-80.
