Exhaustion has its way of making us disregard every bedtime ritual, and after a long night out, it becomes very tempting to make a beeline straight to your pillow. But allowing yourself to go even one night without washing you makeup off first could be the difference between healthily aging skin and prematurely aging skin. One woman, with the help of a high resolution cameras, wanted to see what wearing makeup for a month without washing it would do, and “The Doctors” TV show was on it.

The talk show showed pictures of a woman whose face was continuously caked with makeup. After a month of forgoing facial nightly washes, the effects were obvious. Her facial lines were deeper and her face became inflamed and splotchy. “Her skin biologically looked a decade older after this experiment,” host Dr. Travis Stork said on the show.

“Washing your makeup off every night is very important. Skipping even a single night can cause your skin to age prematurely for various reasons,” said Dr. Annie Chiu, a dermatologist and correspondent on the show.

For one, airborne pollutants, such as smoke and dirt, can stick to the makeup and cause oxidative stress in the skin. In other words, the makeup and added pollutants can make it difficult for skin cells to detoxify, causing them to become damaged. What’s more, Dr. Chiu said that leaving makeup on may also reduce the production of collagen, which provides structural support for skin, helping our skin “look youthful and plump.”

Makeup can also create a barrier in the skin, preventing irritants from escaping and moisture from entering. “This exacerbates redness and irritation, increases pore size, deepens wrinkles—all those things that make our skin appear older,” Dr. Chiu said.

She recommends washing makeup off nightly with a gentle cleanser and applying moisturizer. “Your skin repairs itself at night, so removing makeup gives your skin a clean palette for applying your nighttime performance products for maximum absorption,” Renee Rouleau, an esthetician said in a blog post.