What to patch test
Patch test the product, not the stone. Anything new that you plan to use as a slip should be tested first: facial oils, serums, balms and moisturizers. This matters most if your skin is sensitive or you have reacted to products before. The stone itself rarely causes problems. The exception is metal, since some people react to nickel, which some stainless steels contain.
A simple at-home patch test
- Read the label first. Follow any patch test directions the maker gives, and skip products that contain an ingredient you know you react to.
- Pick a small patch of skin that is easy to see and won't be washed often, such as the inside of the forearm or the skin just behind the ear.
- Apply a small amount of the product, about the size of a coin, to the same spot.
- Repeat once or twice a day for several days, as you would use it. Many dermatologists suggest about a week for a leave-on product.
- Check the patch each day for redness, itching, stinging, bumps or swelling.
If the patch stays calm through the test, try the product on a small area of the face, such as the side of the jaw, before using it all over.
If you get a reaction
- Wash the area gently with lukewarm water and stop using the product.
- Don't use the product on your face, even diluted.
- Note the product name and ingredients, which helps a dermatologist if it happens again.
- If the reaction is severe, spreads, blisters, or affects your eyes or breathing, get medical help promptly.
What a patch test can't tell you
A home patch test is a simple precaution. Facial skin can be more sensitive than the forearm, so a product can pass on the arm and still bother your face, and some reactions take time to appear. If you react to products often, a dermatologist can do formal patch testing, which checks for specific allergies under controlled conditions.
A note on oils
Plant oils are natural products, and natural doesn't mean gentle for everyone. Some people react to particular plant oils or to essential oils and added fragrance. A plain, fragrance-free product is a sensible place to start, and a patch test still applies. The same goes for homemade blends.
Testing the tool too
You can try the tool itself on the inside of your forearm before your first session. A few slow strokes with slip show you how the edge feels and how little pressure you need. Then follow the preparation steps and the technique guide. If your skin reacts easily, read the sensitive skin page first.