You should always check the expiration date on your products — a lesson one woman learned the hard way.

A TikTok doc has shared the sometimes graphic results of using expired skin care products, showcasing a woman who badly burned her skin after contracting a bacterial infection.

Board-certified plastic surgeon Dr. Anthony Youn, who goes by @DoctorYoun on TikTok, called attention to the plight of a woman who goes by @BeastEater on TikTok.

The woman posted several videos showing people the gnarly infection she got after using expired acne and dark spot treatments on her face.

Dr. Youn reposted the woman’s videos three days ago as a cautionary tale to his 8 million-plus followers.

He said that after putting on the expired product, her skin “started to burn, so she washed it off and steamed her face afterward.”

“As you can see, she developed some severe partial thickness and even almost a full-thickness burn up there,” he said as he pointed to the skin between her eyes.

She waited four days before going to the hospital where doctors diagnosed her with a bacterial infection that could have gotten into her bloodstream, Dr. Youn explained.

Luckily, she fully healed from the infection, but Dr. Youn had a word of advice: “Please don’t apply expired products to your face.”

In the comments section of the video, Dr. Youn explained why expired products can cause this kind of reaction.

“When products expire their chemical composition can change and they can accumulate bacterial growth, both may contribute to her reaction,” he said.

The Post reached out to Dr. Youn for additional comment.

Several commenters below his post thanked him for the advice and said they feared they had expired products in their drawers.

“Some products do not have expire dates. There are some products I barely use so how do I know when to stop using that product,” one person said.

“Some of my face masks are years old I’m scared,” another added.

“Wow. Great video, Doc. I never would have thought this. Expired skin care I would have assumed just looses its efficacy. Thx for posting,” a third said.

Dr. Youn isn’t the only medical professional to warn against using expired products.

“The biggest risks of using expired skincare products include loss of efficacy and irritation from degrading ingredients,” Dr. Ivy Lee, a board-certified dermatologist practicing in Los Angeles, told Business Insider.

The Mayo Clinic also warned against using expired skin products as well as cosmetics and said it’s a common misconception that expired makeup is safe to use.

“Risks are associated with using expired makeup, including clogged pores and bacterial growth. It’s important to be mindful of how long your makeup has been in storage so you can avoid these potential health hazards,” their website read.

“Your skin may react to product ingredients if they have reached their expiration date. This could lead to redness or irritation. If bacteria get into an open container or onto a brush, they can multiply rapidly and cause breakouts or other infections,” they continued.