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Patch Testing Specialist

Magnolia Allergy and Asthma

Allergy, Asthma, & Immunology Physician located in Dallas & Corsicana, TX

If you ever had poison ivy or developed a rash after wearing rubber gloves, you’ve experienced allergic contact dermatitis. When you keep developing itchy rashes and other skin symptoms, the only way to diagnose the source of the problem is with patch testing. Monica Sandhu, DO, at Magnolia Allergy and Asthma has helped many patients find relief for contact dermatitis with patch testing, followed by treatment that targets their allergen. To schedule an appointment, call one of the offices in Dallas or Corsicana, Texas, or use the online booking system.

Patch Testing Q&A

What is patch testing?

A patch test is a type of skin test used to diagnose allergic contact dermatitis and to identify the substance causing your allergic reaction. Dr. Sandhu also uses a patch test to diagnose metal allergies in patients with orthopedic implants or who need implants.

What causes allergic contact dermatitis?

Allergic contact dermatitis occurs when your immune system is hypersensitive to a substance that touches your skin, leading to an allergic skin reaction. You may develop a reaction the first time you’re exposed to the allergen, or your allergy may build up gradually over years of coming into contact with the substance.

Substances that often cause allergic contact dermatitis include:

  • Metals (nickel and cobalt)
  • Plants (poison ivy, oak, and sumac)
  • Fragrances (in perfumes, soaps, lotions, and other products)
  • Topical medications (especially antibiotics)
  • Preservatives (in skin-care products and topical medications)
  • Rubber or latex (in adhesives, balloons, and gloves)

You can also develop allergic contact dermatitis from the dyes used to color fabrics.

What symptoms develop due to allergic contact dermatitis?

Allergic contact dermatitis causes a variety of skin symptoms:

  • Red, itchy bumps
  • Red, inflamed skin
  • Burning or itching
  • Blisters that ooze
  • Dry, scaly skin
  • Raised itchy patches (hives)
  • Swelling under your skin (angioedema)

Patients with ongoing inflammation and itching can develop areas of dark, leathery skin.

What happens during patch testing?

Prior to your patch test, Dr. Sandhu talks with you about how to prepare. It doesn’t require a lot of planning or effort, but you need to take a few steps, such as avoiding sun exposure to your back for several weeks before the test.

Patch tests require three separate appointments. During your first appointment, Dr. Sandhu applies one or more patches to your skin, usually on your upper back, but possibly in another location like your arm.

Each patch is a strip of material that can hold 10 different allergens. The patches stick to your back with an adhesive, securely holding the allergen against your skin. 

Contact allergens cause a delayed response, so you wear the patch for 48 hours, then return to the office so Dr. Sandhu can check your skin for allergic reactions such as redness, inflammation, or swelling.

You continue to wear the patch for 3-4 additional days, giving your body more time to have a reaction. Then you return for your third appointment where Dr. Sandhu checks your skin again, talks with you about your results, and develops your treatment plan. 

If you develop a skin rash, call Magnolia Allergy and Asthma or book an appointment online.