Diagnosis

Patch testing for contact dermatitis

Matthew Hall, M.D.: Patients can get allergic to various things that they are using, such as soaps, lotions, makeups, anything that contacts the skin.

DeeDee Stiepan: Nickel, which is often used in costume jewelry, is the most common allergen. So how can someone know if they're having an allergic reaction to something they're putting on their skin?

Dr. Hall: Patch testing is the crucial test that we perform to assess for allergic contact dermatitis. It's a weeklong test. We have to see patients on Monday, Wednesday and Friday of the same week.

DeeDee Stiepan: During the initial visit, the dermatologist determines possible risk factors that may be causing the contact dermatitis.

Dr. Hall: Then, based on that, we customize a panel of allergens for each patient that are placed on these aluminum discs that are taped onto the back.

DeeDee Stiepan: After two days, the patient comes back to get the patches removed.

Dr. Hall: But we also have to see the patient back on Friday because it can take 4 to 5 days before we see reactions. So it's a weeklong commitment.

DeeDee Stiepan: At the end of the week, patients are provided with a list of what they're allergic to.

Dr. Hall: We also give them access to a customized database of products that are safe for them to use that do not contain the substances that they are allergic to.

DeeDee Stiepan: For the Mayo Clinic Newsnetwork, I'm DeeDee Stiepan.

Your health care provider may be able to diagnose contact dermatitis by talking to you about your signs and symptoms. You might be asked questions to help identify the cause of your condition and uncover clues about the trigger substance. And you'll likely undergo a skin exam to assess the rash.

Your health care provider may suggest a patch test to identify the cause of your rash. In this test, small amounts of potential allergens are put on sticky patches. Then the patches are placed on your skin. They stay on your skin for 2 to 3 days. During this time, you'll need to keep your back dry. Then your health care provider checks for skin reactions under the patches and determines whether further testing is needed.

This test can be useful if the cause of your rash isn't apparent or if your rash recurs often. But the redness indicating a reaction can be hard to see on brown or Black skin, which may lead to a missed diagnosis.

Treatment

If home care steps don't ease your signs and symptoms, your health care provider may prescribe medications. Examples include:

  • Steroid creams or ointments. These are applied to the skin to help soothe the rash. You might apply prescription topical steroids, such as clobetasol 0.05% or triamcinolone 0.1%. Talk with your health care provider about how many times a day to apply it and for how many weeks.
  • Pills. In severe cases, your health care provider may prescribe pills you take by mouth (oral medications) to reduce swelling, relieve itching or fight a bacterial infection.

Lifestyle and home remedies

To help reduce itching and soothe inflamed skin, try these self-care approaches:

  • Avoid the irritant or allergen. The key to this is identifying what's causing your rash and staying away from it. Your health care provider may give you a list of products that typically contain the substance that affects you. Also ask for a list of products that are free of the substance that affects you.
  • Apply an anti-itch cream or ointment. Put on the itchy area 1% hydrocortisone cream or ointment (Cortizone 10, others). This is a nonprescription product that you can buy at a drugstore. Use it 1 to 2 times a day for a few days. Or try calamine lotion. Whatever product you use, try cooling it in the refrigerator before applying.
  • Take an anti-itch drug. An oral antihistamine, such as diphenhydramine (Advil PM, Benadryl, others), which may also help you sleep better. A nonprescription antihistamine that won't make you so drowsy is loratadine (Alavert, Claritin, others).
  • Apply cool, wet compresses. Place a cool, wet cloth over the rash for 15 to 30 minutes several times a day.
  • Protect your skin. Avoid scratching. Trim your nails. If you can't keep from scratching an itchy area, cover it with a dressing. Leave blisters alone. While your skin heals, stay out of the sun or use other sun protection measures.
  • Soak in a soothing cool bath. Soak the affected area in cool water for 20 minutes. Sprinkle the water an oatmeal-based bath product (Aveeno).
  • Protect your hands. Rinse and dry hands well and gently after washing. Use moisturizers throughout the day — on top of any medicated cream you're using. And choose gloves based on what you're protecting your hands from. For example, plastic gloves lined with cotton are good if your hands are often wet.

Preparing for your appointment

You're likely to start by seeing your primary care provider, who might then refer you to a doctor who specializes in skin disorders (dermatologist).

Because appointments can be brief, it's a good idea to be well prepared for your appointment.

What you can do

  • List your signs and symptoms, including when they began and how long they've lasted.
  • Avoid any substances that you think may have caused the rash.
  • Make notes about any new products you've started using and any substances that regularly come in contact with your affected skin areas.
  • Make a list of all the medications and supplements you take. Even better, take along the original bottles and a list of the dosages and directions. Include any creams or lotions you're using.
  • List questions to ask your health care provider.

For contact dermatitis, some basic questions you could ask include:

  • What might be causing my signs and symptoms?
  • Are tests needed to confirm the diagnosis?
  • What treatments are available, and which do you recommend?
  • Is this condition temporary or chronic?
  • Can I wait to see if the condition goes away on its own?
  • Will scratching spread the rash?
  • Will popping the blisters spread the rash?
  • What skin care routines do you recommend to improve my condition?
  • How can I prevent this in the future?

What to expect from your doctor

Your health care provider is likely to ask you questions such as the following:

  • When did you begin noticing symptoms?
  • How often do you have symptoms?
  • Have your symptoms been continuous or occasional? Do they get better over the weekend or during vacation?
  • Does anything seem to make your symptoms better or worse?
  • Have you started using any new soaps, lotions, cosmetics or household products?
  • Does your work or a hobby involve using products that often come in contact with your skin?
July 01, 2022
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