How to patch test skincare before using it

To patch test a new skincare product, put it on a quarter-sized spot on the underside of your arm or the bend of your elbow, twice a day, for seven to 10 days. If the spot shows no red, itchy or swollen skin by the end, the American Academy of Dermatology (AAD) says to go ahead and use the product. The test matters most for products with an active ingredient, such as salicylic acid, benzoyl peroxide, adapalene, retinol or glycolic acid. This page follows the AAD method step by step and adds what the FDA allows acne product labels to say. For where a new product fits in your routine once it passes, see the complete acne skincare routine.

Why test before your whole face

A product can suit one person and irritate another. The AAD says that even when you choose products for your skin type, you can still end up with one that irritates your skin. An ingredient such as a preservative can trigger allergic contact dermatitis, which makes skin red, itchy and swollen. Testing on a small area first "can help predict" whether you will have a reaction.

The NHS describes contact dermatitis as skin that becomes itchy, blistered, dry and cracked, usually within a few hours or days of contact with the cause. It lists cosmetics among the products that can trigger the allergic type. A reaction on a small spot of arm is easier to live with than one across your whole face.

The AAD method, step by step

1. Pick the spot. Choose a quarter-sized area where the product won't be rubbed or washed away, such as the underside of your arm or the bend of your elbow. Use skin that is healthy, with no cuts, sunburn or rash.
2. Use the normal amount. Apply the same amount and thickness you would use every day, the AAD says. A larger amount does not make the test more accurate.
3. Leave it on as you normally would. A cream, gel or sunscreen stays on. A cleanser or mask that you rinse off stays on for five minutes, or as long as its instructions say. The same goes for a shaving cream, as shaving with sensitive skin explains.
4. Repeat twice a day for seven to 10 days. Some reactions only appear after the skin has met a product several times, so one application is too short a test.
5. Read the result. No red, itchy or swollen skin after seven to 10 days means the AAD's answer is to go ahead and use the product.

Keep other new products off the test spot for the whole test. If you test two things on one patch and it reacts, you will not know which one caused it.

The 3 day test on acne product labels

The FDA rules for over-the-counter acne products (21 CFR 333.350) allow a label direction called a "Sensitivity Test for a New User." It says to "apply product sparingly to one or two small affected areas during the first 3 days." If no discomfort occurs, you follow the rest of the label.

This test uses the skin you plan to treat, so it shows how your face handles the product. It is optional text, so some labels print it and others leave it out. You can do both tests: the AAD arm test first, then the 3 day test on a few spots on your face.

The same FDA rules require every benzoyl peroxide and salicylic acid label to warn that "skin irritation and dryness is more likely to occur if you use another topical acne medication at the same time." A patch test cannot remove that risk. It shows only how your skin handles one product on its own.

What a reaction looks like

The AAD lists three signs: red skin, itchy skin and swollen skin. If you see any of them, gently wash the product off as soon as possible and do not use it again. A cool compress or petroleum jelly can calm the spot. If the reaction is severe and a cool compress or petroleum jelly does not help, the AAD says you may need to see a dermatologist.

The Drug Facts label for Differin adapalene gel names the signs of an allergic reaction: itching, a rash, hives, swelling of the lips or eyelids, and shortness of breath. The label says to stop use and ask a doctor if any of these appear, or if irritation becomes severe.

Some signs need emergency help. The NHS says to call 999 if your lips, mouth, throat or tongue suddenly become swollen, or if you are struggling to breathe. In the US, the number is 911.

Retinol and acids can sting during the test

The AAD says that some ingredients, such as retinol and glycolic acid, can irritate your skin, most of all sensitive skin, and calls this irritation "normal and temporary." The adapalene label says the same about adapalene: redness, itching, dryness and burning are more likely in the first few weeks, and irritation usually lessens with continued use. Retinol for sensitive skin and vitamin C serum for sensitive skin explain how to start those products slowly.

So a retinoid test spot that turns dry or pink during the first days can still pass. Hives, a rash, swelling, or irritation that keeps getting worse are the signs to stop. If you cannot tell which one you are seeing, stop the product and ask a pharmacist or doctor. How to start adapalene covers a slower start that makes the first weeks easier to handle.

What a patch test does not show

The AAD test looks for red, itchy or swollen skin. The AAD does not describe it as a test for clogged pores, and your arm is not the skin you plan to treat. To lower the chance of new pimples from a moisturizer, sunscreen or makeup, the AAD advises using only products labeled "non-comedogenic" or "won't clog pores." You can check a product's ingredient list with the comedogenic checker.

A home test also cannot always find the cause of a rash. The AAD says that when it is hard to find the ingredient that makes your skin react, a board-certified dermatologist can help, and you may need a medical test called patch testing. On its page about that test, the AAD explains that the dermatologist places small amounts of allergens on your back under patches, you leave them on for 48 hours, and you return after 4 to 7 days, because an allergic reaction can take time to develop.

One new product at a time

The AAD's advice for adult acne is to use one product for 6 to 8 weeks and not add another product during that time. Its page on acne that won't clear adds that "trying too many products can stress your skin, worsening acne." Patch testing follows the same idea: test one product on each spot, read the result, then move to the next.

Some acne routines start two treatments together on purpose. The UK NICE guideline (1.5.1) lists "a fixed combination of topical adapalene with topical benzoyl peroxide for any acne severity" as a first-line option, and the 2024 AAD guideline lists combining topical treatments that work in different ways as good practice. If you plan to start two acne gels at once, test each one on its own spot, so a reaction points to one of them. NICE (1.5.7) also says to start these treatments on alternate days, or to wash them off after an hour, to lower irritation.

You do not need to test a product again if your face has used it for weeks without trouble. Test again when the formula changes or the strength goes up, for example from 2.5 percent to 5 percent benzoyl peroxide, because that is a new product for your skin.

Once a product passes, what order to apply your acne products shows where it goes, morning and night. If a treatment that passed the test seems to cause new pimples in the first weeks, skin purging vs a real breakout explains how to tell the two apart. Skinli's sample plan shows how two acne gels are started together, every other night for the first 2 weeks.