02-07-2025
How To Patch Test a New Skincare Product Correctly, According to Dermatologists
It's an all too common scenario: You're excited to try your new skincare product, whether it's an eye cream, serum, moisturizer, or body cream, and slather it all over, only to find yourself with a rash a few hours later. The reality is that skin reactions do happen, but there is an easy way to avoid them—patch testing.
'It's a good idea to patch test products when using them for the first time, especially if you have sensitive skin, to identify any adverse reactions before you apply the product to a larger area,' says Dendy Engelman, MD, FACMS, FAAD, board-certified cosmetic dermatologist and Mohs surgeon at the Shafer Clinic in New York City. 'It's a safer way to ensure a product is compatible with your skin before regular use.'
Now you're probably wondering, what is patch testing exactly? To help break down the procedure, we turned to two dermatologists to get the scoop, including the best way to do it at home. Below, learn everything there is to know about patch testing. Dendy Engelman, MD, FACMS, FAAD, is a board-certified cosmetic dermatologist and Mohs surgeon at the Shafer Clinic in New York City.
Kseniya Kobets, MD, is the Director of Dermatology at Montefiore Einstein Advanced Care.'Dermatologists or allergy doctors often use patch testing to determine if a specific ingredient or substance can be causing someone to have rashes or skin reactions from contact with the skin, skincare, or the environment,' says Kseniya Kobets, MD, Director of Dermatology at Montefiore Einstein Advanced Care. The test is applied in the office and includes a series of 'patches' of concentrated allergens that come into direct contact with the skin. This is typically applied as a bandage with six to twelve patches per strip. "It's checked over a few days to a week to check for a reaction or delayed reaction on your skin after exposure to common and reported allergens," explains Dr. Kobets.
While the in-office treatment is recommended by experts, you can also try to patch test at home. According to Dr. Kobets, you should apply a small amount of a cream or other topical you'd like to test to the inner part of your arm and monitor if it causes a reaction within hours to 24 hours. However, she warns that this is not a precise method. At-home testing involves using a product that can contain various ingredients. If you do have an allergy, you wouldn't know which component is causing the reaction. In-office patch testing, on the other hand, uses individually identified allergens at higher concentrations, which are more likely to show a reaction and offer a more targeted result.
It's best to do a patch test every time you try a new hair or skin product, especially if you have sensitive skin or a history of atopic dermatitis or eczema. 'It's also important to test products that contain active ingredients or fragrances, which are more likely to cause irritation,' says Dr. Engelman. 'Patch testing is best done at least 24 to 48 hours before using the product widely, to give enough time to spot any reaction.'
If you choose to perform a patch test at home, Dr. Engelman shares these step-by-step instructions:
Choose a small, discreet area of skin to test, such as behind the ear, the inner forearm, or your foot.
Apply a small amount of the product to that spot, spreading it thinly and evenly.
Cover the area with a bandage or leave it uncovered if the product dries quickly.
Wait at least 24 to 48 hours without washing or disturbing the spot.
Check the area for any signs of redness, itching, swelling, or irritation.
If there's no reaction, the product is likely safe to use on your skin.
If irritation appears, avoid using the product and consult a dermatologist if needed.
After completing these steps, it is important to take action should a reaction occur. 'It will be easy to tell if a patch test reveals an adverse reaction—you'll likely notice redness, itching, small bumps, and/or unusual warmth, which can signal early irritation,' Dr. Engelman says. 'If your patch test causes a reaction, stop using the product right away and gently wash the area with cool water and a fragrance-free cleanser. Applying a gentle, fragrance-free moisturizer can help soothe the skin. If the reaction gets worse or doesn't improve in a day or so, consult your dermatologist for guidance.'
It's important to note that you can still have a delayed reaction even if your patch test showed no immediate issues. 'Some sensitivities develop slowly and may only appear after repeated or prolonged use of a product,' Dr. Engelman says. 'The patch test checks for quick reactions but doesn't always catch long-term irritation or allergies. Always watch your skin closely when trying something new, even after a clear patch test.'
If you have a history of reactive skin and it is only getting worse over time, then Dr. Kobets suggests getting a professional patch test in consultation with a dermatologist.
As far as what to expect during a professional patch test, the process is fairly straightforward. A dermatologist will typically apply standard allergens on your back unless you already have an active rash, acne, or reaction on the area. 'You're advised to avoid exposure to sun and moisture, avoid scratching, and to come back at a specific time throughout the week for the first reading at 48 hours and then a second reading at 72 to 96 hours,' Dr. Kobets explains.
Your dermatologist or allergist may ask you to avoid specific medications, such as antihistamines and topical or oral steroids, for a specific number of days before the testing, as they can interfere with the results, adds Dr. Kobets. 'You may want to keep a list of products you're allergic to or sensitive to, and note a common unifying ingredient that reappears in all of these,' she adds.
If you have sensitive skin or suspect a new product may trigger a reaction, patch testing is a good idea. Going the DIY route can be fine, but keep in mind that it won't always accurately predict a reaction. 'You should see a professional for a patch test if you have persistent or severe skin reactions that don't improve with home care,' Dr. Engelman says. 'It's especially important if you experience widespread redness, swelling, blistering, or intense itching after using products. A dermatologist can perform a more thorough patch test to identify specific allergens or irritants. They can also recommend personalized treatment and help you avoid triggers in the future.'
Read the original article on Byrdie
