How to Patch Test Skincare at Home

To patch test a skincare product, apply your normal amount to a quarter-sized spot on the inner arm or the bend of the elbow twice a day for seven to 10 days. That is the method the American Academy of Dermatology (AAD) recommends S01. Leave a leave-on product in place as you normally would, and keep a wash-off product such as a cleanser on for about five minutes before rinsing. If the spot stays free of redness, itching and swelling for the whole period, the product is less likely to cause a reaction. If a reaction appears, wash it off and stop using it S01.

Why patch testing is worth the time

Any skincare product can irritate skin, even one chosen for your skin type. Sometimes an ingredient such as a preservative triggers allergic contact dermatitis, which makes skin red, itchy and swollen S01. Testing on a small area first helps predict whether that will happen before the product goes on your whole face S01.

Label words do not answer the question for you. The FDA says there are no federal standards or definitions for "hypoallergenic," and the term means whatever a particular company wants it to mean S02. The same is true of "fragrance-free" and "for sensitive skin": the FDA notes there is no federal standard or definition for those terms in the U.S. S03. A test on your own skin is more informative than any claim on the box. For more on label wording, see fragrance-free vs unscented and natural does not mean safer.

How to patch test skincare, step by step

1. Pick the right spot

Choose a quarter-sized area where the product will not be rubbed or washed off during the day. The AAD suggests the underside of the arm or the bend of the elbow S01. Pick skin that is clear of rashes, cuts or eczema so you can see any change.

2. Use your normal amount

Apply the product as thickly as you normally would S01. A very thin smear can miss a reaction that a normal layer would cause.

3. Match how you would normally use it

• Leave-on products (moisturizer, serum, sunscreen, makeup): leave on for as long as you normally would S01.
• Wash-off products (cleanser, mask, scrub): leave on for about five minutes, or as long as the instructions say, then rinse S01.

4. Repeat twice a day for seven to 10 days

A single application is not enough. Allergic skin reactions can be delayed, which is why even medical patch tests are read days after the allergen goes on S03. The AAD recommends applying the product to the same spot twice daily for seven to 10 days S01.

5. Watch and record

Check the spot each morning and evening. Note the date, the product name and batch or lot number, and anything you see: redness, itching, swelling, bumps or flaking. A written record helps if you react later and need to work out which product was responsible. Our purchase log has space for this.

6. Decide

If after seven to 10 days there is no reaction, go ahead and use the product as normal S01. If there is a reaction, see the next section.

What counts as a reaction

If you react, gently wash the product off as soon as possible and do not use it again. A cool compress or petroleum jelly can soothe the skin. If a reaction is severe and does not ease with those measures, a dermatologist can help manage it S01.

Special cases

Active ingredients

Retinol and glycolic acid can irritate skin, particularly sensitive skin. The AAD describes this as normal and temporary S01. When patch testing an active, look for redness or itching that builds over several days, rather than brief tingling.

The AAD also suggests starting with one new product at a time S04. If you add three at once and react, you will not know which one caused it.

Eczema-prone skin

People with eczema may need a longer test. In AAD guidance on eczema, a dermatologist suggested testing new products on a quarter-sized patch on the inside of the arm every day for four weeks S05.

Hair dye

Hair dye has its own rules. The FDA advises a patch test on your skin every time before dyeing your hair with a coal-tar hair dye, following the directions in the package S06. Use those package instructions, not the skincare method above.

Patch testing at home vs at a dermatologist

At-home patch testing checks one product. Medical patch testing looks for the specific ingredient you are allergic to.

The FDA describes medical patch testing this way: a small amount of possible allergens is placed on the skin and covered for 48 hours, and a physician checks the skin after 72 to 96 hours. It usually takes two to three office visits S03.

Consider seeing a board-certified dermatologist if:

• You react to several products and cannot work out the common ingredient S01.
• A reaction is severe or keeps coming back.
• You have active eczema or dermatitis, which can make results harder to read S03.

Once you know the cause, avoiding it gets easier. The AAD gives fragrance as an example: if fragrance causes a reaction, choose products labeled "fragrance free" and be careful with "unscented" products or products with plant-based botanical ingredients, which may still contain fragrance-related ingredients S01.

Common ingredients behind cosmetic allergies

The FDA groups the substances that cause most cosmetic allergic reactions into five classes: natural rubber (latex), fragrances, preservatives, dyes and metals S03. Preservatives the FDA lists include methylisothiazolinone (MIT), methylchloroisothiazolinone (CMIT) and formaldehyde-releasing ingredients such as DMDM hydantoin, diazolidinyl urea, imidazolidinyl urea and quaternium-15 S03.

The FDA's advice is to know what you are sensitive to, read the ingredient list, and avoid ingredients you know or think you react to S03. The FDA requires an ingredient declaration on cosmetics sold at retail to consumers S03. Our guide to reading a skincare label walks through where to find it.

If you think you have had a reaction to a cosmetic, you can report it to the FDA S03.

A simple patch test record

Keep one line per product:

• Product name, brand, size and lot number
• Date started
• Test spot used
• Morning and evening notes for each day
• Result and date you decided

This takes a minute a day and saves guesswork later.

Frequently asked questions

How long should you patch test skincare?

The AAD recommends applying the product twice a day for seven to 10 days. People with eczema may be advised to test for longer, up to four weeks.

Where is the best place to patch test?

A quarter-sized spot on the underside of the arm or the bend of the elbow, where the product will not be rubbed or washed away.

Can you patch test on your face?

Start on the arm. The AAD advises testing a product on the inner forearm before applying it to your face, and moving to the face only once the arm test is clear.

How do you patch test a cleanser?

Apply it to the test spot, leave it on for about five minutes or as long as the instructions say, then rinse. Repeat twice a day for seven to 10 days.

Does "hypoallergenic" mean I can skip the patch test?

No. The FDA says there is no federal standard for "hypoallergenic," so it can mean whatever the company wants. Testing on your own skin is more reliable.

What should I do if I react to a patch test?

Wash the product off gently, stop using it, and use a cool compress or petroleum jelly to soothe the skin. If the reaction is severe or does not improve, see a board-certified dermatologist.