Itching to Understand Allergic Contact Dermatitis and Skin Allergies
Understanding Allergic Contact Dermatitis
by Merry Thornton, PA-C
Allergic contact dermatitis (ACD) is an itchy skin condition that occurs when your skin comes into contact with a substance to which you have developed a sensitivity. ACD is often a confusing diagnosis, as you can develop skin allergies to a something that you have tolerated for many years.
What are the symptoms of ACD?
ACD can present in different ways. Symptoms include redness, itching, blisters, red bumps, leathery skin, swelling, and inflammation. The reaction is usually localized to areas that are exposed to the allergen. For example, if you have a nickel allergy and wear earrings containing nickel, the earlobes may be red, dry, and itchy. However, it is not always that straightforward. Airborne droplets of allergens in fragrances, cleaning products, hairsprays, etc. are common causes of eyelid dermatitis. When substances are released in the air, they can settle on vulnerable areas, such as the eyelids, and cause a reaction.
Symptoms rarely appear on immediate contact. It may take hours or days to have a reaction. If this is the first time your skin reacts to that substance, you may not notice a reaction for weeks. However, once you have been sensitized, you will react to that substance with subsequent exposure, even in low concentrations of the allergen.
What are common causes of ACD?
The top ten allergens as identified by the North American Contact Dermatitis Group are listed below with examples of where they may be found.
Nickel: A metal used in jewelry, buckles, clothing snaps, dyes, and surgical instruments.
Neomycin: An antibiotic used in topical creams, powders, ointments, eye and ear drops.
Balsam of Peru: An aromatic liquid found in certain fragrances (perfumes, deodorants, cosmetics), flavorings (citrus peels, cola, spices), and topical medications (wound spray, insect repellent, throat lozenges, lip preparations, mouthwash).
Fragrance: Found in skin care products, perfumes, medications
Thimerosal: Preservative in vaccines, antiseptics, contact lens solutions, and cosmetic products.
Gold: Used in jewelry, dentistry, and electronics.
Quaternium 15: A compound found in hand and face creams, lotions, shampoos, latex paints, polishes, adhesives, and inks.
Formaldehyde: An organic compound used as a preservative, disinfectant and antiseptic. Found in dyes, textiles, leather hides, cosmetics, nail polishes, shampoos, deodorizers, glues, paints, plastics, adhesives, dry-cleaning, and fertilizers.
Bacitracin: An antibiotic used in topical creams, powders, ointments, eye and ear drops.
Cobalt: Found in paints, alloys, dental fillings, glass, zippers, and utensils.
How do I determine what is causing my allergy?
Finding the cause requires a bit of detective work. Your provider will take a detailed history to help determine what is causing the rash. Patients will often try to eliminate products or limit exposure to possible culprits, but a procedure called patch testing is the best way to pinpoint the allergen. At Schweiger Dermatology Group, we use the North American 80 Comprehensive Series, which contains 80 of the most common allergens. The patches are applied to the back with tape and removed after 48 hours. The site is evaluated for redness, blistering, and pustules, which if present, indicate a reaction. The site needs to then be reevaluated 24 to 48 hours later, as some allergens may take longer to produce a reaction. You should avoid getting the back wet during patch testing.
How can I be allergic to my deodorant/shampoo/detergent/fill in the blank? I have used it my whole life without a problem!
This is confusing to patients, and rightly so. It is hard to imagine that you could develop an allergy out of thin air. I like to bring up my experience with poison ivy. As a child, I used to play in a tree house. All the other kids would end up getting a raging rash, complete with blisters, oozing, and intense itching, while I would be fine. Then one day last summer I was gardening and finally found out what a reaction to poison ivy felt like. I developed a delayed hypersensitivity reaction; consequently, every time I come into contact with poison ivy, I get an itchy rash. Once you develop an allergy to a substance, even a small amount of it can cause a reaction. This is what is meant by an “acquired sensitivity.”
What is the difference between patch testing and prick testing?
Prick testing is used to detect hypersensitivity reactions involving immunoglobulin-E (IgE)-mediated release of histamine, while patch testing is used to identify delayed hypersensitivity reactions, which are mediated by T cells, not IgE. In plain English, a prick test would be appropriate for a suspected allergy to food, pollen, mold, or animals, while patch testing would be applicable for a suspected allergy to substances that touch the skin such as cosmetic products, metals, and dyes.
I am only using “unscented” and “hypoallergenic” products. Why am I still developing a rash?
Fragrances can be used to create a pleasant scent but may also be used to mask an unpleasant scent. These products may be labeled as “unscented.” Instead, look for products that say “fragrance free” (although “fragrance free” products can even have fragrance compounds!).
“Hypoallergenic” usually means that the product contains fewer allergens than other products of its kind. These products are designed to minimize the possibility of an allergic response. However, It is not a term that is regulated by the FDA and these products may still contain ingredients that result in contact allergies. When in doubt, look at the list of ingredients to determine whether the allergen is included in the product.
How do I treat my ACD?
ACD is typically treated with topical steroids. In severe cases, oral steroids may be necessary. Symptomatic treatments such as cool compresses can also provide relief. Wet dressings may be recommended for oozing skin, while antibiotics may be prescribed for secondary infections that can result. The definitive treatment for ACD is the identification and elimination of the offending agent. Once your allergy is identified, your dermatology provider can recommend safe products and help you avoid ones that contain the substance that affects you.