Bad hair day? Yeah, it actually might be because of your period.

Bad hair days happen to all of us—right?—we’re in a hurry for work; slept on it wrong and no matter what we do, we can’t fix it; and it looks worse during our menstrual cycles… What?!

“Although we mostly think of skin as being most reactive to the hormonal, and other, changes of the menstrual cycle, the fluctuations of the menstrual cycle can, in some cases, directly and indirectly affect the scalp and hair,” said dermatologist Sophia Kogan, MD, of Nutrafol, to Refinery29.

Yes, our hormones affect our hair. Just like we feel better on some days during our cycles and worse on others, our hair has feelings, too—good days and bad days. But, not all of us may be affected. If you’re on hormonal birth control, your hair may be like NBD versus if you’re using non-hormonal birth control methods.

Refinery29 made a little cheat sheet about how our cycles sync up with our hair. Here are the highlights, so you know when it’s best to wash and dye your hair or just let it be.

Ovulation

This is a great time for your hair, so take it out and show it off. This is due to high estrogen levels and low testosterone ones. Since you’re about two weeks away from your period at this point, the estrogen causes the production of a hormone called the luteinizing hormone, aka LH. As a result, your hair and scalp may get a bit more oil, which is a good thing in this case.

Before Your Period

Our hair’s had better days. Now, it may be more oily and our complexions may suffer, too. Experts recommend using dry shampoo and also say it’s a great time to dye your hair, if that’s your thing. “There are myths that say oily hair can affect processing results, but this is untrue,” hairstylist Anna Costa of The Rittenhouse Spa & Club – Hair by Paul Labrecque, told Refinery29. “Having slightly oilier hair actually can help protect the delicate skin of the scalp from the chemicals as they sit on your hair.”

During Your Period

I know, who likes this stage of the game?! Aside from taking care of our non-hair needs, we need to give our hair some attention, like dry shampoo on an as-needed basis. But, it’s an optimal time to avoid any big changes to our hair, like the dyeing we should have done during our pre-menstrual cycle.

After Your Period

You’ve been through a lot the last few weeks, and so has your hair. So, your hair may need some extra TLC, like deep conditioning treatments, especially if it seems drier than usual. Experts also recommend possibly washing it less—thanks to less oil production, which is thanks to less testosterone and more estrogen—and applying hair serum to your ends in between. In any case, have no fear, ‘cause you’ll be at the ovulation stage again before you know it, just in time to take your hair back out on the town.

To get ALL the details about period hair, check out the Refinery29 rundown on the subject.