When it’s that time of the month, your body can go through unpleasant and uncomfortable changes - just ask anyone who’s had a period. In a recent video, supermodel Chrissy Teigen proved that celebrities are no exception.

Teigen shared a video of herself on Twitter saying, “This is my skin on my period. Look at it. So angry. Ow,” as she pointed to red blemishes on her cheeks and the tip of her nose.

Read: Do Periods Sync Up With Friends? Plus 4 Other Things That May Affect Your Menstrual Cycle

Her post quickly gained attention and has been retweeted more than 20,000 times since Monday afternoon. Both men and women have praised her for being so open about the reality of the side effects that come along with your period. “As a father of 2 young girls, it’s reassuring to see a LITERAL model who is comfortable in her own imperfections. A sincere thank you!” one user commented.

“Love the way you are so bloody authentic. The best compliment I can give a person imo. You rock CT. And are an adorable gal,” another user wrote.

Read: Can Exercise Help Acne? How Relieving Stress Can Improve Your Skin

But, what exactly is “period skin” and why does it happen?

Just like cramps, changes in your skin, such as blemishes and blotches, are a completely normal and common side effect of your monthly cycle. Various types of hormonal shifts happen during a cycle causing women, especially those who are acne-prone, to experience a flare-up of blemishes.

“As levels of progesterone increase, skin swells and pores are compressed shut,” dermatologist Audrey Kunin told WedMD. This causes the pores to appear minimized. “But this tourniquet effect also causes sebum to build up beneath the skin’s surface.”

Sebum is an oily, waxy substance that acts as a natural way to waterproof and lubricate your skin. “For some, [sebum] produces a healthy glow; for others, it creates a chronic oil slick,” Kunin said.

Although acne isn’t completely preventable, practicing a good skincare routine, including daily washes and visiting a dermatologist for treatment, can help.

See also: 5 Causes For Sudden Adult Acne: Why Hormones, Stress, And More Can Cause Skin Breakouts

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