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When your skin comes into contact with substance in the environment that you are allergic to, it may react by causing your skin to itch and become red. This is called contact dermatitis.
There are many types of contact dermatitis. The three most common types are irritant, allergic and contact urticaria (hives).
Irritant contact dermatitis is the most common type of contact dermatitis. It can develop quickly when the skin touches an irritating chemical, is rubbed too hard, or comes in contact with heat. These substances break through the skin barrier and can cause inflammation.
If the skin is already open with a wound, or if you have active atopic dermatitis, it is much easier for these irritants to enter and cause irritant contact dermatitis.
Allergic contact dermatitis is the second most common contact dermatitis type. Unlike, irritant contact dermatitis, the skin can take 48 to 96 hours to develop a reaction.
The first time the skin comes in contact with a new allergen, it sends a piece of the allergen off to the immune system for analysis and storage in the immune system’s memory bank, but does not cause a reaction. This process is called sensitization.
When the skin comes into contact with the substance over and over, the immune system “remembers it” and develops an itchy skin response. Because it can take a few days for the immune system to recognize the chemical, the skin symptoms may be appear several days after actual exposure.
Contact urticaria, also known as hives, is a less common form of contact dermatitis. With contact urticaria, swelling and redness usually happen right away after the skin comes in contact with an irritating substance. It is usually not long-lasting.
There is rare but serious risk of an anaphylactic reaction (a severe allergic reaction that causes the throat to swell, chest tightness, and other symptoms) that can coincide with contact urticaria. If you think you are having an anaphylactic reaction, contact your doctor immediately.
Irritant contact dermatitis usually stays on the skin where the exposure to the allergen occurred. If the exposure is to a strong irritant, an immediate reaction including pain, swelling and sometimes blistering can be present. If there is ongoing exposure to a mild irritant such as water or soap, the reaction can occur over a period of weeks to months and involve dryness, itching and cracking.
Allergic contact dermatitis may also be limited to the site of original contact, but more often spreads. The skin becomes red, hot, itchy and may “weep.”
Contact dermatitis can sometimes be very difficult to distinguish from atopic dermatitis, another form of eczema. Your doctor can help you with a correct diagnosis.
The skin signs and symptoms of contact dermatitis may appear similar to those of atopic dermatitis.
There are many different causes or triggers for contact dermatitis.
Irritant contact dermatitis may develop from everyday substances such as water, too much pressure or friction on the skin and weather changes such as extreme temperature and humidity.
There are a large number of potential allergy-producing chemicals. Here are some common ones:
Nickel allergy is extremely common among adults and children. Nickel is found in a range of metallic items, such as jewelry, zippers, buttons, belt buckles and coins. It is also found in some less obvious places like, cell phones, white gold, some orthopedic joint replacements and certain foods.
Cobalt is found in metals, including nickel, and people allergic to nickel are often allergic to cobalt because of its widespread use. Cobalt is also used in personal products such as hair dyes and antiperspirants.
Chromium salts, often found in paints, cement, and leather products may cause allergic contact dermatitis and sometimes irritant contact dermatitis symptoms.
Fragrances are common triggers of ACD especially in people with damaged skin barriers, such as with atopic dermatitis. These substances can be found in various cosmetics, perfumes, food flavorings and toothpastes.
Antibacterial ointments such as neomycin and bacitracin are often used to treat everyday scratches and wounds, but some people develop allergic reactions.
Formaldehyde is a preservative. It is also a top adult and child allergen. Formaldehyde is in many places including household disinfectants, vaccines, glues and adhesives, cigarette smoke and embalming fluid.
Formaldehyde-releasing preservatives are in personal care products such as cosmetics and may trigger some individuals who are allergic to formaldehyde. Hidden sources of formaldehyde include “permanent press” and “wrinkle- resistant” clothing and the artificial sweetener, aspartame.
Isothiazolinones, including methylchloroisothiazolinone and methylisothiazolinone (MCI/MI) are used in many personal care products to prevent bacteria from growing and protect the product from oxygen and light damage. They are often found in many “wash-off” items such as shampoos, body washes and cosmetics. As well, they are found in some wet wipes, baby wipes and moistened toilet tissues.
Cocamidopropyl betaine (CAPB) is a detergent used to thicken shampoos, soaps and lotions, and reduce static cling in clothing.
Paraphenylene-diamine (PPD) is a strong chemical used in hair-dye. It is not allowed in products that are meant to touch the skin due to the allergy potential.
Nevertheless, PPD continues to be used in various unregulated products for the skin such as temporary tattoos. PPD is often used to dye shoes black, and can cross-react with dyes used in clothing and some medications, such as antihistamines.
Patch testing is an important tool to diagnose allergic contact dermatitis. In this test, selected chemicals put on an adhesive strip, or “patches” and applied to the back, where there are no symptoms.
The patches are left on for 48 hours. After 48 hours, the doctor removes the patches and looks at the skin for reactions. After two more days, the doctor looks at the patch sites for signs of inflammation. If there is inflammation, the allergy to that particular chemical is confirmed.
The best treatment for contact dermatitis is avoidance of the substance that caused the reaction. Keep a careful record of when a CD flare-up happens and what products you were using prior to the outbreak. Read labels for common irritants and eliminate those from your household. Look for items with the NEA Seal of Acceptance™ as these have been created for sensitive skin.
Some providers who often treat contact dermatitis subscribe to electronic programs that create shopping lists for people with allergies, such as the Contact Allergen Management Program (CAMP) and the Contact Allergen Replacement Database (CARD). Ask your health care provider if they subscribe.