Many of us have that favorite tube of lipstick or that favorite blush compact that we swear by. And as tempting as it might be to hold on to them forever, it’s important to know when to say goodbye. Keeping your favorite products around too long can lead to a number of unwanted reactions, such as acne or even an eye infection. Below is a list of the most common beauty products and their shelf-life.

1. Mascara — (3 months) According to the American Optometric Association (AOA), mascara should be replaced every three months because of the likelihood that it will collect bacteria with prolonged use. Holding on to mascara and other eye makeup longer than three months can increase the risk of eye and/or skin irritation or infection (to your face, eyelids, etc.), according to Dr. Debra Jaliman, dermatologist and author of Skin Rules: Trade Secrets From a Top New York Dermatologist.

2. Eye shadow — (18 months) If you’re using your eye shadow correctly, as in using clean brushes, not touching it with dirty fingers, and storing them in a non-humid place, you can probably get a longer use out of it. Similar to mascara, it is very easy for bacteria to grow on products like this. However, sometimes, as the eye shadow gets older, it can start to crumble and break, but that doesn’t necessarily mean it needs to be tossed.

3. Foundation — (12-18 months) This one is important because using old foundation can actually cause skin issues, especially if you’re using it with a dirty makeup brush or sponge. Water-based foundation can last up to 12 months and oil-based will last up to 18 months, check the back of the bottle for a list of ingredients. Also, be diligent with cleaning the makeup tool that you use to apply your foundation.

4. Lipstick — ( 2 years) You can increase the shelf-life by storing your lipstick in the refrigerator. If you’re prone to cold-sores, using a disposable applicator can protect you from them. The amount of water in lipsticks can also make them a perfect breeding ground for bacteria to thrive.

5. Eyeliner — (3 months or 2 years) Liquid eyeliners, can tend to dry up fast, depending on how frequently they are used, so tossing them out every three months is your best bet. Being that they are liquid, there is an increased risk of developing bacteria. Pencil eyeliners can last up to two years.

6. Powders and Blush — (2 years) Powders usually have a stronger shelf-life because they contain little water, which decreases the likelihood of bacteria forming. Be sure to place your powders and blushes in a cool and dry location.