There’s nothing worse than picking up a new makeup product only to realize that the color or formula doesn’t work for you. Because some brands are a bit on the pricier side, it can be a major bummer to figure out that you’re never going to use a specific product. That’s why testing them first can be a huge asset. Even if you’re buying online, product reviews can be a big help. Here’s how to test all kinds of makeup safely and effectively.

The importance of safety
When you’re testing products, it’s essential to keep safety in mind. Sharing cosmetics is never a good idea, and that’s especially true for in-store samples. Dr. Elizabeth Brooks, a biological sciences professor at Jefferson Medical College in Philadelphia, conducted a study recently on public makeup testers. “We went to department stores, specialty stores, drugstores – everywhere,” she explained. Her researchers found staph, strep and even E. coli bacteria on lipstick, blush, mascara and moisturizer testers.

Luckily, there are ways to be safe about the samples you test. For example, Glamour Magazine recommends asking the salesperson to prep the tester for you. This involves dipping lipsticks in alcohol, then scraping off the top layer and using a new, disposable applicator. Eyeliners and lip liners can simply be sharpened to remove the contaminated surface layer. Powders and creams can be wiped with an alcohol wipe and the surface can be removed. It’s never a good idea to try something that comes in a pot, as people dip their fingers into it, contaminating the entire jar.

It’s also better to shop on weekdays, when fewer people will be trying out the products. Saturdays are the worst, and according to Brooks’ findings, Wednesday and Friday mornings are the best, as they found less contaminated products on these days.

Lastly, avoid putting any makeup on your lips or eyes, which are the most likely places where bacteria and viruses can enter your body and cause infections or disease.

How to test each product
For foundation: When sampling a product, don’t test it on your jaw, suggests Allure Magazine. The color of your neck is more uniform than your face, so put a bit of product there to get the most accurate match.

For concealer: Test out shades on your inner wrist. Go with the one that you think best matches your skin tone, then try one shade darker and one shade lighter just to be sure. You might want to purchase two different shades: one peachy-pink for undereye circles and one with yellow-based tones to cover blemishes.

For blush: Test blushes on the back of your hand, but put a bit of foundation on it before you head to the store. The product sticks differently to skin that’s completely bare, and you want the same effect that your face will get.

For highlighter: The best highlighters illuminate without any obvious glitter or shimmer, so test these products on the back of your hand to ensure that you can’t see any flecks.

For bronzer: Test these out on your inner arm, suggests Allure Magazine. It should look like a natural tan, so don’t choose anything with shimmer. If you can see freckles underneath the formula, it will look natural on your face – if not, skip it.

For eyeshadow: Use an applicator to apply to the back of your hand and your inner wrist. When you move your hand around, the product shouldn’t crease. Keep in mind that a primer can keep any shadow in place.

For lipstick: Try out new shades on the pads of your fingertips for the most accurate sense of how the color will appear on your lips.