Patch Testing

Patch testing is used for allergic reactions on your skin. For example, if you develop a rash after using a new shampoo or wearing a new piece of jewelry. This test can identify what causes contact dermatitis, a red, itchy rash caused by direct contact with a substance. Some patients who have contact dermatitis will have an immediate reaction on the skin when they come in contact with a particular allergen. 

Patch testing can detect delayed allergic reactions which in some cases may take days to develop. So our allergists will leave the patch on for about two days to see if you have any allergic reactions. We will also ask you to return later in the week to check for any delayed reactions.

When patch testing, we apply specific substances that cause allergic inflammation of a patient’s skin, such as metals, detergents, and even fragrances. Indicating sensitivity when irritation develops such as faint redness to severe itchiness. 

What Substances Are Tested With Patch Testing? 

● Hair dye 

● Preservatives 

● Cosmetics 

● Medications 

● Nickel, Gold, and Cobalt 

● Mercury 

● Silver, Beryllium, Chromium 

● Perfumes 

● Other Fragrances 

Patch testing does not test for urticaria (hives) or food allergy. While wearing the patch, try to avoid activities that make you sweat as this can affect results. Certain cortisones can also affect testing. This test is not recommended for those with long-term skin conditions, such as eczema. 

What To Expect During Patch Testing

During the patch testing, small amounts of the allergen will be placed on your skin and covered by a patch for 48 hours. During this time you may experience itchiness or soreness. Other symptoms due to a late reaction might include pain and swelling. You should refrain from scratching and confirm with our NYC allergists what medications can help relieve some of your symptoms. It is important that you do not remove, lift or wet the patch for accurate results. 

After the first 48 hours, you will return to your allergist and they will remove and treat the reaction. Then you will return to your allergist again after 4-7 days. This appointment is essential to detect any delayed reactions. One of our allergists will provide you with a personalized treatment plan. Your treatment plan will include specific medications and explain how to avoid your allergies.

Patch Testing Frequently Asked Questions

Are Patch Tests Uncomfortable? 

The patch testing procedure is simple and painless. However, you may experience some itching.

Can I Shower During the Patch Test?

You cannot shower until after your Allergist removes the patch test after 48 hours. On day 2 of the test, your allergist will remove the patches. If lifting occurs before day two, apply tape.

Can I Sleep On My Back During Patch Testing?

Try to sleep on your stomach or side and avoid sweating as much as possible. Also, do not expose your back to sunlight during the day.

Is Patch Testing Accurate? 

As with any kind of skin testing, patch testing is not 100% accurate. False negatives may occur, meaning you didn't react to that trigger or indicating a contact reaction when you do not have one. 

What Do I Need to Know For the Patch Test? 

Avoid sun exposure for at least 1-2 weeks prior to the patch testing. Try not to use topical medications such as ointments and creams on the patch testing area for at least one week prior to the patch testing. 

What Do You Wear For Patch Testing?

Consider wearing shirts that open at the front, rather than the ones you have to pull over your head. Try to wear that shirt for the rest of the week. 

What Happens If You Scratch During A Patch Test? 

Despite the itchiness, try to refrain from scratching the patch test area. Scratching may irritate the skin and cause the itch to grow worse, making it hard to interpret your test results.

What Happens If Your Patch Test Is Negative? 

A negative patch test result means you are not allergic to the most common contact allergens and allergen mixes. Six of ten people who have a patch test have negative results. 

What Is A Positive Reaction To A Patch Test? 

A positive test result indicates your skin will have an adverse reaction to that allergen. 

What Should I Avoid Before A Patch Test?

All topical creams and ointments should be avoided including vaseline and lotions. Refrain from applying to the patch area at least 24 hours prior to the patch testing.  

What Should I Do After Patch testing?

Unless your NYC allergist applies water-resistant cream on the patch area, you should minimize exposure to water. Even after the removal of the patches, you should limit showering and avoid scrubbing the test site until the final reading.