Im stepping into 2020 with the healthiest hair Ive ever had, beauty influencer Brittanie Evans recently posted on Instagram, touting her partnership with SugarBearHair supplements. Celebrities like Kylie Jenner, Vanessa Hudgens and Gwyneth Paltrow have also credited hair vitamins for their luxurious locks.

But, do hair vitamins actually work? It depends, says New Orleans-based dermatologist Mary Lupo.

She compares hair supplements to chicken soupthey cant really hurt and may help. But, if you have a medical condition causing hair loss or other hair issues, hair vitamins likely wont help, and medical treatment may be needed.

What I think is important is that a person kind of go through a little checklist and make sure that before they spend money on vitamins, that theyve ruled out other things that can cause the problem, she says.

You may wish your hair was thicker or shinier or that it would grow longer more quickly. There are several reasons why your hair may not be cooperating.

Stress is a big one: Cortisol is your stress hormone, and a lot of women lose hair or shed hair, or their hair doesnt grow as long because of stress, Lupo says.

Stress can cause a condition called telogen effluvium, a scalp disorder that leads to hair shedding or thinning. It often occurs after instances of stress on the body, like surgery, illness or having a baby, Lupo says.

Other reasons you have issues with your hair:

Some conditions actually damage the hair follicle, Lupo says. Cicatricial alopecia, for example, is caused by scar tissue in the hair follicle, making hair fall out, and its usually irreversible. Alopecia areata is an autoimmune disease, causing quarter-sized chunks of hair to fall out.

Genetics also play a role in hair loss or conditions that cause it.

Hair loss because of chemotherapy could benefit from hair vitamins, Lupo says.

When you have hair loss from chemo, your hair has to cycle back and maybe the hair vitamins can speed it up a little bit, she says. I dont think its going to be anything earth-shattering, but I dont think it would hurt and it might help a little bit.

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For someone without a medical condition, vitamins could improve hair, but it will take time, six months or more to see a result, Lupo says. Thats because hair follicles grow in cycles.

According to the Cleveland Clinic, the anagen, or growing, phase, may last two to eight years, and refers to most of the hair you have. The catagen phase, which takes two to three weeks, refers to the timeframe when hair follicles shrink. The telogen, or resting, phase is when the hair falls out and can take two to four months.

If your hair cycles into the telogen phase too quickly, it may not grow as long as youd like, since once the hair sheds, and the process starts all over again, Lupo says. Seeing results from hair vitamins depends on taking them regularly for several months.

One month isnt going to make any difference at all, she says. Then, once you see the result, what I tell my patients is you can lower the dose of the vitamin. Like if it tells you to take four a day, you could cut it down to two a day or whatever as a maintenance dose after youve taken it for about a year. But, dont discontinue it or youll lose the benefit.

When shopping for hair vitamins, read the list of ingredients to ensure they contain substances that promote healthy hair: B vitamins, especially biotin, and vitamin E promote hair, nail and skin health, Lupo says.

The way vitamins help hair is really more from the antioxidant or anti-inflammatory (standpoint) to make the scalp healthier and the hair follicle healthier, she explains.

Many hair vitamins also contain plant-based ingredients, like ashwagandha and saw palmetto, which encourage hair health.

Ashwagandha has been shown to lower cortisol and also has anti-inflammatory properties, which promotes healthy hair. Saw palmetto is an ingredient in may products for men that helps with hair loss and prostate cancer.

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The U.S. Food and Drug Administration(FDA) does not review supplements, including hair vitamins, for safety before theyre allowed on the market. Lupo says hair vitamins are generally safe, though.

She suggests reviewing a hair vitamin products list of ingredients and choosing ones without too many additives. Also, look for ones that are Good Manufacturing Practice (GMP) certified, like the Natures Bounty brand.

Finally, be wary of any hair vitamins that make medical or any too-good-to-be-true claims.

I think that theyre safe for anybody, Lupo says. Its just the danger is if you have a medical condition that is undiagnosed and unrecognized that is causing you to lose your hair. If youre just taking vitamins, you might be wasting your time and your money, and youre not getting a proper diagnosis so that you can get appropriate treatment.

Along with hair vitamins, prescription drugs like Propecia and Rogaine can help treat hair loss, Lupo says, but women shouldnt take Propecia unless they are postmenopausal.

Dermatologists may also use platelet-rich plasma (PRP) therapy injections to trigger hair follicles to grow more hair. Lupo says usually four to six sessions of PRP are needed, and need to be repeated after several months to maintain results.

PRP is pretty much considered the gold standard of a therapeutic option, Lupo says. Its perfectly safe because you take your own blood, its spun down, you extract the platelets, and its injected into the scalp.

Diet also improves hair quality. Eating plenty of protein, omega-3 fatty acids, and fruits and vegetables, especially dark green veggies, can make your hair thicker and shinier.

If you have hair loss, thinning or other problems, Lupo suggests visiting your dermatologist to rule out any medical problems, even before trying hair vitamins or if youve tried hair vitamins with no results.

I would urge a person if theyve got a real hair loss problem to get the appropriate evaluation by a dermatologist and any recommended blood work that the dermatologist gives you sooner rather than later, she says.

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