How Does Patch Testing Work?

Feb 13, 2024
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Allergy experts use a variety of methods to get to the bottom of allergic reactions. Are you having a skin allergy? Here’s why they might suggest a patch test, and what you can expect from this screening.

Some allergies can be obvious to detect, like your lips, tongue, or throat swelling after eating something. Or even just dreading the first signs of spring because of hay fever.

However, other allergies can be less obvious, especially those involving the skin. That’s where patch testing can help.

Our experts at Allergy, Asthma, & Immunology Associates use several screening methods to diagnose allergies. 

Here’s how a patch test works and when we use this assessment at our Tampa and Brandon, Florida, locations.

How allergy testing works

Allergic reactions occur when your immune system perceives something harmless as a threat. Things you eat, breathe, or touch can trigger these responses, which vary in severity.

Allergy testing can safely confirm the specific substance that prompted your reaction. There are different tests that can offer more definitive insights, depending on the suspected allergy.

For instance, we could suggest a skin-prick test to identify an allergen that is causing an immediate reaction. Or, if you have a skin condition or a powerful allergen that is causing a significant response, we could turn to blood tests.

However, if we suspect your symptoms have developed in response to something you’ve touched, we often recommend patch testing. 

When to use a patch test

Skin-prick and patch testing often get confused. However, they work in different ways.

During a skin-prick test, we make a tiny opening in the skin so the suspected allergen can penetrate the body. With a patch test, we simply expose the surface of your skin to the substance.

Patch testing offers numerous benefits, especially when diagnosing an allergic reaction that develops over days instead of instantly. 

These types of allergies often occur from things people are exposed to on a daily basis, such as:

  • Personal products, like cosmetics, fragrances, hair dyes, or essential oils
  • Jewelry, like cobalt or nickel
  • Products with latex, like gloves or condoms
  • Medications

Exposure to these types of substances often causes contact dermatitis, or an inflammation and rash. 

A patch test can ascertain if your skin reaction is due to irritation or an allergy.

What to expect from a patch test

Unlike a skin-prick, patch testing takes time. Fortunately, most of it is waiting for a response to occur.

The process starts with an office visit. During your appointment, your provider applies small amounts of suspected allergens to your skin. Then, they cover them with a patch. We can test for numerous allergens at one time, so you could have multiple sites with patches.

Once we finish, you head home and leave the patches in place for 48 hours. You should avoid showering, bathing, and sweating during this time frame.

If you notice your skin becoming itchy, burning, or tender during this time, it could indicate a reaction. However, you should leave the patches in place as instructed. If serious discomfort occurs, contact our office.

When the initial 48-hour testing period ends, you return to our office so we can remove the patches and inspect the area. Since it can take time for these reactions to develop, you could need an additional reading 2-7 days later.

If an allergy is present, the area often becomes red, swollen, and itchy. You could also develop small blisters. These symptoms typically clear up within a few days. However, this test could trigger a psoriasis flare-up in those with that skin condition.

Once we reach a diagnosis, we can determine the best method for managing your condition moving forward.

Are you having persistent or recurring skin problems? Call Allergy, Asthma, & Immunology Associates or book online to schedule a consultation with one of our experts in Tampa or Brandon today.