Patch Testing

Table of Contents

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