It is always recommended that you do a patch test before applying a new product all over your face. Although serious allergic reactions are rare, they do still happen and you don't want to wake up with a swollen puffy face because you simply didn't patch test a product. So here's how to do a easy patch test on yourself. Apply a small amount of selected product on your upper forearm. Rub in slightly and wait 30min. Look for any signs of redness, itching, stinging Do not use if you have any sign of irritation. Always do this before putting a new product on your face. You could also apply a few drops behind the back of your ear instead of your forearm.