People may feel horny before their period because of their hormonal cycle. Our hormone levels fluctuate depending on the phase of our menstrual cycle. The hormones testosterone and estrogen are linked with sexual desire. Estrogen will begin to peak during ovulation, says reproductive endocrinologist Sheeva Talebian, M.D., and testosterone also surges. That means the desire to have sex usually increases around the ovulatory phase, which starts about 14 days before menstruation and might last until about seven days before.

"People with vaginas are most fertile when we ovulate, and that spike in testosterone charges up our body to desire sex," writes functional health coach Erin Rachel Doppelt, M.A., who tracks her menstrual cycle with her partner and encourages other couples to do the same. "During this time, I feel sexy," she says. "Typically my skin is a bit more oily, my hair is shiny, and my odor is different—more sweet and tangy. Because I'm looking and feeling more attractive than ever, my partner and I like to get it on during this time."

Some people also feel particularly horny during their period. That may be because of the increase in blood flow to the pelvic and genital regions, says Gilberg-Lenz. More circulation to these areas may make them more sensitive and more engorged (similar to how more blood flow to the penis is what helps get an erection going), stimulating those sensitive nerve endings and triggering arousal.

There may also be psychological reasons behind a higher libido during your period. "For those who have a rough PMS, the sheer relief of menstruating could play a role," Gilberg-Lenz says. The relief of not being pregnant (increased stress has been linked to low libido11) may also contribute to an increased desire, she says.

Your vagina is also getting natural lubrication in the form of menstrual blood, which might trigger arousal for some folks.

Evolution might also have a role to play here, OB-GYN Heather Irobunda, M.D., tells mbg.

If you're feeling extra horny right before or during your period, that's completely normal. This could be caused by your hormonal cycle, relief of not being pregnant, or the natural lubrication of menstrual blood.