How to patch test makeup
Reading the Label · ingredientlogic Editorial · 3 min read
The short answer
A patch test is a small, deliberate exposure to one product on one spot of skin, left alone for 24 hours, so that a reaction has a single obvious cause. Test the full formula rather than a suspected ingredient, use one product at a time, and write down the list you tested, not the brand.
Why patch test a whole formula rather than one ingredient?
You almost never meet an ingredient alone. What touches skin is a formula, and reactions can come from a combination rather than a single line on a list. Testing the finished product is the only test that matches the way you will wear it.
Keep the list you tested. Two products from one brand can run on entirely different formulas, so a note that says the brand name tells you very little six months later.
How long should a patch test run?
Twenty-four hours, undisturbed. Irritation often shows within an hour, but delayed responses are common enough that a short test can read as a false clear.
Step by step
- 01Pick one product and one spotUse the inner forearm, or just behind the jaw if you want a spot closer to facial skin. One product per test — two at once means an unreadable result.
- 02Apply a normal amountA patch about the size of a coin, applied the way you would wear it. A smear thinner than real use can under-report irritation.
- 03Leave it for 24 hoursDo not wash the area, layer anything over it, or scrub it. If it stings sharply or burns at any point, remove it and stop the test.
- 04Read it in daylightLook for redness, raised skin, itching, or small bumps that stay after the product is removed. A faint pink that fades within minutes of washing is usually friction, not a reaction.
- 05Write down the formula, not the brandNote the product name and the full ingredient list on the day you tested it. Formulas change; your record should say which one you actually wore.
- 06Repeat before the next new productIntroduce one product at a time, several days apart. Adding three at once makes a reaction impossible to attribute.
Common questions
