A doctor's viral TikTok video shows why you should avoid applying eyeliner to your waterline

• Dr. Brittani Carver-Schemper shared a TikTok video warning against using eyeliner on the waterline.
• She says wearing makeup this way can clog special glands and lead to dry-eye disease.
• The TikTok of a patient having their eye glands unclogged has nearly 13 million views at the time of writing.

A doctor is urging people to stop putting eyeliner on their waterline, and her TikTok explaining why has gone viral.

Dr. Brittani Carver-Schemper, an optometrist from Fayetteville, North Carolina, posted a video on July 15 warning her 204,000 TikTok followers about the dangers of wearing eyeliner on the waterline. The video, which features a patient of hers getting her eye glands unclogged, has since gotten nearly 13 million views.

In the TikTok video, Dr. Carver-Schemper is seen using an extraction tool to unclog the eye of a patient who has worn eyeliner on her waterline since she was a teenager. Narrating the video, the doctor explains that there are special glands on the waterline of the eye that secrete oil.

In normal cases, the secretion is supposed to have an "olive oil" texture to it. But when eyeliner is repeatedly put on the waterline, according to the optometrist, the oil can become more like "toothpaste."

Dr. Carver-Schemper, who has practiced medicine for 20 years, said: "The reasons eye doctors do not recommend to wear eyeliner on the waterline of your eye is because there are specialized glands there that produce and excrete oil."

When the oil isn't its usual texture, she said that means the glands are "obstructed" and "not producing healthy tears."

In an email to Insider, Dr. Carver-Schemper went into more detail about the long-term consequences of having these glands blocked.

She said the glands in the waterline of the eye "produce and secrete our tears' oil layer that protects the tear film and keeps our tears healthy."

"Without good quality oil and healthy tears, we will develop dry-eye disease that could affect our vision and cause discomfort to our eyes," she added.

"We see many patients that wear eyeliner on their waterline, and almost all of them have some degree of gland damage," Dr. Carver-Schemper said. "We need to avoid applying liquid or pencil eyeliner to that area to keep our eyes healthy."

She also explained that other factors, including using your phone or tablet, can lead to dry-eye disease. "Blinking helps excrete oil from the glands in our eyelid," she said. "When we focus on computers and electronic devices, our blink rate decreases by 60%, leading to thickened oil and blocked glands."

Marisa Garshick, a board-certified dermatologist from New York, told Insider that the glands Dr. Carver-Schemper are referring to are known as "meibomian glands."

"When makeup is applied to the area known as the waterline, it can potentially block the glands known as meibomian glands that release an oily substance that contributes to the tear film, which can subsequently lead to dry eye or irritation," Garshick said.

But according to Garshick, there are actually some products that are "formulated with waterline application in mind, so when applied properly, they may be less likely to cause problems."

She also referenced a small pilot study she'd seen, which found that putting eyeliner on the lower lash line was more likely to contaminate the tear film.

However, Garshick did also say the study had an important result. "Any contamination was thought to be temporary as the eyes had returned to pre-application levels two hours later," the dermatologist said.