How to Prepare for Allergy Patch Testing

If you’re dealing with ongoing skin irritation, rashes, or dermatitis, your provider may recommend an allergy patch test to identify the root cause. Unlike other allergy tests that detect food or airborne triggers, patch testing is specifically designed to identify delayed skin reactions caused by substances like fragrance, metals, latex, or chemicals.

At BASS Medical Group, our primary care providers work with allergy and immunology specialists to help patients find answers and relief from chronic allergy-related symptoms.

What Is an Allergy Patch Test?

An allergy patch test is a non-invasive procedure that helps identify contact allergens that may be triggering delayed skin reactions. It’s commonly used to diagnose conditions such as:

• Allergic contact dermatitis
• Eczema
• Reactions to personal care products, metals, or topical medications

During the test, small patches containing different allergens are applied to the skin—usually on your back—and left in place for 48 hours. Your provider will evaluate the skin at two intervals: once when the patches are removed, and again at the 96-hour mark. A positive result appears as redness, bumps, or small blisters.

Up to 80–100 allergens can be tested at once.

How to Prepare for Patch Testing

To ensure accurate results, your provider may recommend the following before your test:

1. Stop Taking Antihistamines

Avoid taking antihistamines for at least 72 hours prior to your appointment. This includes over-the-counter medications like:

• Benadryl (diphenhydramine)
• Claritin (loratadine)
• Zyrtec (cetirizine)
  Some acid reducers (like Pepcid) also have antihistamine properties, so check labels carefully.

Always consult your provider before stopping any prescribed medications, especially beta-blockers or antidepressants.

2. Avoid Topical Steroids

Don’t apply corticosteroid creams or ointments (like hydrocortisone) to your back for at least 3 days before testing.

3. Limit Sweating

After the patches are applied:

• Avoid showering or bathing for 48 hours
• Refrain from heavy exercise or anything that causes excessive sweating
• Wear loose, breathable clothing to prevent the patches from dislodging

Sweat and friction can interfere with how well the patches adhere and affect the test’s accuracy.

Who Might Need an Allergy Patch Test?

You may benefit from patch testing if you have:

• Chronic rashes that don’t improve with treatment
• Recurring eczema, especially in specific areas like wrists, neck, or eyelids
• Skin reactions after using cosmetics, lotions, or cleaning products
• A suspected nickel or latex allergy

Your provider will determine if patch testing is the right next step based on your symptoms and medical history.

Other Types of Allergy Tests

In addition to patch testing, your doctor may recommend:

• Skin prick test: Checks for immediate reactions to pollen, pet dander, mold, and foods
• Blood allergy test (IgE test): Useful for patients who can’t stop medications
• Food or drug challenge: Carefully monitored tests for food and medication reactions

Patch testing focuses specifically on delayed skin reactions, not food or seasonal allergens.

Post-Test: What Happens Next?

After the final patch removal and evaluation (usually at 96 hours), your provider will discuss any positive results and explain what triggered a skin reaction. From there, they may recommend:

• Allergen avoidance strategies
• Skincare products free of known irritants
• Further evaluation by a specialist if needed

Find Expert Allergy and Skin Care at BASS Medical Group

At BASS Medical Group, our primary care physicians can help evaluate unexplained rashes and refer you to an allergy and immunology specialist if needed. While we do not currently have dermatologists on staff, we collaborate closely with providers who can assess your symptoms and determine whether patch testing is appropriate.

Serving patients in Walnut Creek, Oakland, San Francisco, and the surrounding Bay Area.

Request an appointment or find a provider near you to start your evaluation today.