A report about a cancer-causing chemical being detected in some dry shampoos may have led you rethink your hair care routine.

But experts say there isn’t a one-size-fits-all answer to how often you should wash your hair — or what you can do to maintain it on off days.

“Some people just think that they have to wash their hair every day or they’re going to get very greasy hair,” said Dr. Anthony Rossi, an assistant attending dermatologist at Memorial Sloan Kettering Cancer Center in New York City and a fellow of the American Academy of Dermatology Association.

“If they give themselves a chance, they may see that they don’t actually have that greasy scalp or hair. And on the other hand, they may not be able to tolerate going too long or too infrequently because they feel that their scalp becomes very greasy.”

How frequently you should cleanse your locks depends on multiple factors, including hair type and style, how oily your scalp tends to get, and your activity levels.

“It’s sort of a personal endeavor,” Rossi said. Washing too often can dry and dull hair, while the oil buildup from not washing enough can also lead to odor and flakes.

Here’s how to figure out what works for you.

When to wash

Rossi generally tells his patients they should wash their hair once or twice per week.

But if you’ve had chemical treatments that can make your hair drier — such as bleach, perms or relaxers — you might want to wash it less than once weekly to avoid breaking or brittle hair or split ends, he said.

If your scalp is very oily, you might need to wash it as often as once per day, according to the American Academy of Dermatology Association’s website. Your age can play a role, too.

“During puberty we have this surge in hormones, and so the oil glands can become enlarged. It’s a reason why people get teenage acne,” Rossi said.

Kids might experience more oily scalps during pubescent years, so washing their hair more often could be helpful, he added.

Our scalps produce less oil as we get older, according to the association.

Your hair might be more prone to get dry or break if it’s curly or coily, the association says.

Washing it too often can exacerbate this, so thick, curly hair generally doesn’t need to be washed daily or even weekly, according to the association.

But you should wash it at least every two to three weeks to keep your scalp and hair clean and healthy.

What to do in between washes

Hair and scalp care doesn’t only happen in the shower. In between washes, you can do certain things to maintain its cleanliness and appearance — and protect it from harm.

“I do think it’s important to have scalp hygiene. Just like beard hygiene, you want to take care of the skin that’s underneath,” Rossi said.

“Tend to it and comb (your hair). That loosens up the dead skin cells, the debris. You want to wet it if you can.

“At least massaging your scalp skin will really help to also loosen up debris. So you don’t necessarily have to wash it with a shampoo itself, but keeping it clean is very helpful,” Rossi added.

“You can also use things like leave-in conditioner or scalp oils that help nourish and moisturize the scalp.”

If you regularly sweat from exercising, you don’t need to shampoo your hair every time unless there’s an overgrowth of bacteria or your hair or scalp starts to smell, Rossi said. You can rinse it with water if you want.

Most dry shampoos have been considered safe for hair, but don’t rely on them often, Rossi said.

“If you’re super oily, it’s good in a pinch. But you want to wash that out. You don’t want to build up that on the scalp as well.”

If you notice excess oil just around your hairline, you could wipe it with cosmetic blotting papers, he added.

If you swim in a pool with your hair exposed to the water, chlorine can make it dry and brittle.

Protect your hair by wetting and conditioning it beforehand, wearing a snug swim cap and, immediately afterward, replacing any lost moisture by using a shampoo and deep conditioner specially formulated for swimmers, according to the American Academy of Dermatology Association.

If you’re experiencing perpetual issues with your scalp or hair — such as dandruff, hair loss or brittle hair — you should see a board-certified dermatologist who treats conditions in these areas, Rossi said.