How to patch test a new product

A patch test is a small trial of a new product on a small area of skin before you use it on your face. It takes three nights and almost no effort.

How to do it

1. Apply a small amount to the inside of your forearm or behind your ear.
2. Leave it on as you would normally use the product.
3. Repeat for three nights.
4. If there is no redness, itching or swelling, try it on your face.

Which products to test

Anything with an active: retinal, exfoliating acid, vitamin C. Also test any product if your skin is reactive or you have had a reaction before.

What counts as a reaction

Mild tingling that fades in a minute is common with acids. Burning, itching, hives or redness that lasts are signs to wash the product off and stop.

What a patch test cannot tell you

It does not rule out irritation from using a product too often, and it is not an allergy test. If you have a known allergy, read the full ingredient list first and ask a pharmacist if in doubt.