Historically, doctors have been able to stall or reverse hair loss by prescribing medicine or performing a hair transplant procedure, according to the American Academy of Dermatology. Yet many of these options come with negative side effects, such as sexual dysfunction, an itchy scalp, or a long recovery period, notes the Cleveland Clinic. Minimal side effects are one reason a new treatment called platelet-rich plasma therapy (also known as PRP) has been growing in popularity. Here, learn what PRP is, who it’s best suited for, and the potential risks to be aware of.

What Is the Definition of Platelet-Rich Plasma Therapy?

Doctors first used PRP in medicine in Europe in 2005, says Jeffrey Rapaport, MD, a board-certified dermatologist based in Englewood Cliffs, New Jersey. According to a study published in August 2016 in the American Journal of Clinical Dermatology, PRP helped promote wound healing, often in plastic surgery, orthopedics, and sports medicine. Shilpi Khetarpal, MD, a dermatologist with the Cleveland Clinic in Ohio, says PRP is still often used to help people and athletes bounce back from joint-related injuries, but it wasn’t until five or so years ago that dermatologists started using the therapy to treat hair loss. As of today, the U.S. Food and Drug Administration (FDA) has only approved PRP for use on joints in orthopedic practices, and the first publications including PRP in joints date back to 2005, Dr. Khetarpal says. A paper published in February 2015 in The Journal of Knee Surgery noted that using PRP in any other setting, such as to treat hair loss or skin issues, is considered “off label.” According to the FDA, “off label” means that while the drug or therapy is approved, it’s not approved for the use or diagnosis that your doctor may be recommending. In these cases, the FDA has determined that the drug’s potential benefits may outweigh its risks. Your doctor may recommend an approved drug for an unapproved use if he or she thinks it may be helpful to you, and if you’ve exhausted all other treatment options. RELATED: How to Look Your Best When You Have Hypothyroidism

How Does Platelet-Rich Plasma Therapy Work Exactly?

During a PRP session, a technician draws blood, usually from a patient’s arm. He or she will then spin the blood to extract plasma. Plasma is a substance found in the blood that contains platelets, which promote hair growth, according to the Cleveland Clinic. The technician injects the plasma into areas on the scalp affected by hair loss — usually about 15 to 20 injections per PRP session, Khetarpal says. Though it sounds painful, both Khetarpal and Dr. Rapaport say there aren’t any side effects to worry about. You may experience some mild soreness where the injections took place, but you should be able to bounce back post-appointment. “It’s very well tolerated — more than anything, people just feel pressure,” Khetarpal says. “There’s no anesthetic or anything. People just feel a little bit of tightness and discomfort, and within 30 minutes it’s pretty much done.” PRP doesn’t deliver results immediately, so you shouldn’t expect to see a full head of hair overnight. You’ll likely need three monthly sessions followed by an appointment four to six months later, and then yearly maintenance sessions after that, Khetarpal says. The exact schedule of your treatment plan will depend on a few factors, including the amount of hair loss you’re dealing with, as well as your age, hormones, and genetic makeup, according to the Cleveland Clinic. You’ll likely start seeing regrowth before your third and fourth appointment, Khetarpal says.

What Does Research Say About PRP and Its Benefits?

Though PRP to treat hair loss is relatively new, research has been promising. A small study published in the April–June 2014 issue of the Journal of Cutaneous and Aesthetic Surgery tested PRP on 11 men with androgenetic alopecia who had not had success after six months of medication. After three months, they received four treatments and saw their hair count increase by about 30 percent. A meta-analysis published in September 2017 in the Journal of Cosmetic Dermatology also explored the effect PRP could have on increasing hair number and thickness based on current studies. The researchers found there might be a correlation, but said it was too soon to say because the studies were small and the results weren’t significant. RELATED: What Is Hyperhidrosis? Causes, Symptoms, Treatment

Who Might Platelet-Rich Plasma Therapy Help?

Rapaport says PRP has been shown to help both men and women, mainly those with androgenetic alopecia, which is known among men as male-pattern baldness and among women for leading to thin hair all over the head, according to the U.S. National Library of Medicine. Here are some people who may benefit from PRP:

Balding menWomen who’ve experienced hair loss or thinning hair as a result of menopausePeople who began losing hair within the last five years (Any longer than that and the hair follicles likely have become so small and thin that promoting growth won’t make a difference, Khetarpal says.)

There are also some groups for which PRP may not be good, including those with:

Health conditions that come with hair loss, including lupus or thyroid diseases, like hypothyroidism or hyperthyroidism (People with thyroid problems are not great candidates because hair loss is a result of not only the disease but the medication as well, Rapaport says. In these cases, the hair loss would likely continue even after PRP, according to the Cleveland Clinic.)A history of bleeding disorders, clotting disorders, blood thinners, or hepatitis (These conditions can affect the quality of the platelets, Khetarpal says.)Skin cancer or an active infection on the scalp (Since PRP promotes growth, it could add fuel to the fire if there’s a pre-existing condition, Khetarpal says.)

RELATED: 7 Things Your Hair Says About Your Health

What Are Some of the Possible Downsides of Using PRP?

Overall, PRP is safe and effective. “You’re injecting patients’ own blood and you’re able to reverse something that is devasting for a lot of people,” Rapaport says. “The fact that you have the safety and the efficacy is what makes it really special.” It can be expensive, though. Khetarpal estimates each treatment will cost $600 to $1,500 out of pocket, depending on where you live. That adds up because, to see results, you have to commit to about four treatments in your first year. Khetarpal says FDA-approved medical therapies, including Proscar (finasteride) and Rogaine (minoxidil), are ones she’d turn to first because they “really go after the hormonal component.” She advises patients not to think of PRP as a first-line treatment because it does not address what’s likely causing the hair loss in the first place. “Think of it as giving growth factors to make the hair grow, but it doesn’t address any of the other side — it doesn’t address any of the hormonal or genetic tendencies,” she says. She recommends going to a board-certified dermatologist rather than a plastic surgeon because a dermatologist will be able to offer PRP in addition to medical treatments. Rapaport says PRP isn’t confined to doctors’ offices anymore. You may see it offered as a service at a spa, but Rapaport says to be careful if a thorough consultation isn’t included. He says PRP can be dangerous if technicians are sloppy and aren’t using FDA-approved tubes or aren’t careful about making sure your blood — and only your blood — is injected. RELATED: 10 Things Your Skin Is Trying to Tell You (and How to Respond)

A Final Word Before You Try PRP for Hair Loss Treatment

PRP is an increasingly popular way to treat hair loss. It involves taking plasma from your blood and injecting it into your scalp to stimulate hair growth. The procedure is relatively painless and requires zero recovery time. But it takes a few months to see results and it can be expensive, costing as much as $1,500 per treatment. Khetarpal and Rapaport have both seen positive results among patients they’ve treated, but they stress it’s important to have realistic expectations about what PRP can do. “If [a patient is] in their sixties and wants hair like they had in their twenties, it’s just not realistic,” Khetarpal says. “It’s not going to be perfection. We’re looking for improvement.”