Wearing contacts can be a wonderful alternative to glasses, but it does come with responsibilities. One of them is taking out your contacts each night. In a perfect world, contact wearers do this in the evenings to give their eyes a chance to breathe. However, it’s not uncommon for people to accidentally fall asleep in their contacts.

While it’s okay to sleep in some extended-wear lenses, for the most part, keeping them in your eyes puts you at risk for infection and other problems. If your eyes do become dry, irritated or infected, you will have to stop wearing your contacts until the eyes heal. As some eye specialists say, “The more you wear your lenses today, the less you can wear them tomorrow.”

Let’s check out five things that happen when your contact lenses are left in overnight.

1. Your cornea is deprived of oxygen.

The cornea gets oxygen from the air. Wearing contact lenses decreases this supply, and oxygen is further decreased when the eyes are closed. If you sleep with your contacts in, the cornea can swell and let bacteria sneak in between the eye’s surface cells. This increases your risk of infection.

2. The lenses act as petri dishes.

At night, your body enters a period of rest, repair and recovery. This includes your eyes. However, sleeping in your contacts makes it more difficult for recovery to take place and allows the lenses to act as petri dishes. Any bacteria that is stuck on the lenses will not be washed away by natural tears, leading to a potential infection.

3. You raise your risk of keratitis.

Keratitis is a fancy name for inflammation of the cornea. This condition isn’t anything minor. The Centers for Disease Control reports that over 1 million people in the United States develop keratitis. The vast majority of these cases are due to the improper use of contacts, including sleeping in them.

4. Your eyes become prone to allergies.

Sleeping in your contacts also disrupts healthy blinking. When you blink in your contacts, it creates small abrasions. Over time, the inner lining of the eyelids can become rough. When you combine this with inflammation from overwearing your contacts, it can lead to dry, allergy-prone eyes.

5. You may get a parasite.

Finally, from wearing your contacts overnight, you are putting yourself at risk for a parasite. Acanthamoeba is a parasite found in all water sources. If it gets into the eyes, it can be devastating. Always clean your contacts with a contact solution, never water. Also avoid wearing lenses in pools and hot tubs.

Contacts are thinner, lighter and easier to wear than ever before. But, they still require healthy habits, and that includes taking them out before sleeping. After reading this, we think you will!