Dear Doctor: My skin is red and itchy. How do I know if I am having an allergic skin reaction?
An allergic skin reaction is a common skin rash that occurs when your skin comes into contact with a substance you have an allergy to. It is often called “allergic contact skin dermatitis.” There are other types of allergies, namely those from things you eat (peanuts, for example) or breathe in (pollen and seasonal allergies).
This article will only talk about the rash one gets from substances that touch or “contact” the skin. The most common natural allergic contact dermatitis is from a plant oil found in the leaves of the poison ivy plant.
Allergic contact dermatitis due to (clockwise from top left) poison ivy on the leg, temporary tattoo dye, dye for beards and moustaches, and acrylic nail glue
Why should I care about an allergic skin reaction?
About 15 percent of all people develop a problematic allergic contact dermatitis in their lifetimes.
What causes an allergic skin reaction?
When a contact skin allergy happens, the skin is very purple/red and very itchy. There are thousands of substances that can trigger an allergic contact skin reaction. Commonly, these items can be found in health and skin care products, hair dyes, clothing, jewelry, rubber, leather shoes and boots, cleaning supplies, medical creams and ointments, and industrial chemicals at work.
The most common items that can cause a skin allergy include hair dyes, nickel (found in metal in earrings, watch/jewelry clasps, belt buckles and the nickel button on jeans), fragrances in perfumes and body lotions, antibiotic ointments (polysporin, neomycin), and in preservatives found in many lotions and creams.
Sometimes the location of the rash will give a good hint as to the cause. For example, if the rash is on the lower abdomen, it is most likely from the nickel button on jeans or a big belt buckle. If it occurs on the ears or wrist, it is likely from nickel in jewelry.
If located on the area where one is applying an antibiotic ointment, the medicine is now suspect. If you have a red, itchy scalp after dying your hair, hair dye is the leading suspect.
One tricky thing about allergic skin allergies is that they can occur at any time in response to any product. In fact, the first time you encounter the product you will not get a rash. At the initial encounter your body becomes sensitized to it, with the rash occurring at all subsequent exposures.
Also, products will often change some of their ingredients, such as a fragrance or preservative. So even if you have used “Mrs. Johnson’s skin cream” for 20 years, you can still develop a rash to it at any time.
Remember, any plant like poison ivy, poison oak, sumac and wild parsnip can cause skin allergies. If you get a skin rash after being outside and having plants touch your bare skin, plant allergic contact dermatitis is most likely the culprit.
How is an allergic skin reaction diagnosed?
Your dermatologist may recommend a special allergy test to help make the diagnosis of an allergic contact skin allergy. It is called a patch test because they apply several tiny patches on your back to wear for 48 hours containing the substances that most commonly cause skin allergies. By looking at the reaction of your skin to these patches, your doctor can get the information needed to make the correct diagnosis and give you information on how to avoid that substance in the future.
If you suspect a certain household product for causing your skin rash, you can put a bit of it on your forearm twice daily for five days. If you get no rash there, it probably is not the culprit. If there is a rash, you have made a significant discovery and can review the results with your doctor and avoid that product.
Can an allergic skin reaction be prevented? How is it treated?
The best way to prevent allergic contact skin dermatitis is to avoid the substance that is causing it. For most skin allergies, a topical steroid cream will be prescribed to treat it. Follow your doctor’s instructions very carefully for the best result. For widespread rashes, an oral medication may be prescribed.
Action steps for anyone with an unwanted allergic skin reaction:
If you are having a skin rash that is not relieved by over-the-counter products and you suspect it is an allergy, this is the time to make an appointment to see your dermatologist.
Charles E. Crutchfield III, MD is a board certified dermatologist and Clinical Professor of Dermatology at the University of Minnesota Medical School. He also has a private practice in Eagan, MN. He has been selected as one of the top 10 dermatologists in the U.S. by Black Enterprise magazine and one of the top 21 African American physicians in the U.S. by the Atlanta Post. Dr. Crutchfield is an active member of the Minnesota Association of Black Physicians, MABP.org.