How to test sunscreen to know if i'm allergic to it or not?

Patch test: Put a small amount on the pad of a band aid and attach it to normal skin. Leave it on overnight and check the site.If not red or irritated, you are likely not allergic to it. Those with significant allergy may find it itchy and swollen after a few hours.If so, remove it and wash the area well and apply cortizone (hydrocortisone) cream.