Plumping shampoos, essential oils, DIY scalp scrubs—it seems like there’s no shortage of products and viral TikTok hacks that supposedlythicken strands and stimulate hair growth. Same goes for the seemingly endless list of leave-in treatments for thinning hair. These days, you can’t scroll through Instagram without seeing an ad or two touting the latest-and-greatest “miracle” growth spray or serum, promising to transform thin, lifeless strands into a lush mane with just a few drops.

The over-saturated market makes it hard to figure out what’s *actually* legitimate and what’s not. Which is why we tapped certified hair practitioner, Gaby Longsworth, PhD, a scientist and owner of the website Absolutely Everything Curly, to help suss out what’s serious and what’s potentially just snake oil.

Hair Growth 101, as told by a pro

Longsworth explains that, first and foremost, a healthy scalp is key for hair growth, be it from a leave-in treatment, a shampoo, or a DIY spray you found on Pinterest. Some key ingredients partially enlarge follicles to elongate the overall hair growth phase. “When more follicles are in the growth phase, there are more hair strands on the scalp, and the hair is thicker,” Longsworth says. “Other ingredients work by getting more blood flow and nutrients to the follicle.”

As for the ingredients, she explains that, on the medical side, there are only 1-2 FDA-approved treatments for thinning hair: topical minoxidil and oral finasteride (for men) and topical minoxidil (for women.) This is the key ingredient you’ll find in products like Rogaine.

Natural ingredients that can help promote hair growth

Then, there’s the natural side. Longsworth suggests looking for ingredients that help get blood flow to the hair follicle, such as niacin, arginine, jojoba oil, castor oil, amla oil, and brahmi herbs. “Other ingredients for thinning hair and hair growth include rosemary, antioxidants, biotin, vitamins such as vitamin E, minerals, menthol, peppermint, and salicylic acid,” she says. “And to protect the hair follicle, coconut oil”

What to avoid depends on the type of hair you have. For example, people with thinner hair may want to avoid treatments that are high in oils, since they might weigh down strands. Others might not want the drying effects that eucalyptus or menthol tend to leave on the scalp. 

“Some oils and serums can be ‘heavy’ and make thin hair appear even thinner,” Longsworth says. “Instead, look for lighter leave-ins that are more water-soluble and volumizing, or use smaller, pea-sized amounts of high quality, heavier leave-in conditioners… moderation is key with these products.”

Tl;dr—find what works for you and your hair. And rather than dumping your money into the potentially not-so-great stuff you see on Instagram, start with the list below.

The best (and professionally vetted) leave-in treatments for thinning hair

Davines, Energizing Thickening Tonic — $43.00

Italian haircare brand Davines makes this invigorating thickening tonic that expands the diameter of each hair follicle, giving it a voluminous, plumper look. Its key ingredients are full of the same key vitamins and minerals Longsworth mentions, including antioxidants (from eucalyptus and caffeine), menthol, and key vitamins (pantheol.) Massage onto your scalp, comb through hair, and away you “grow.”

The Innate Life, Rose Hair Elixir — $15.00

“Their Rose Hair Elixir is one of the best,” says Longsworth. “It contains sea buckthorn oil which is rich in vitamins such as vitamin A, C, D, B, E, and K that are necessary for promoting healthy hair. It also contains rosehip oil, which is rich in antioxidants, vitamin A and E, which protect the hair against sun damage.”

Shea Moisture, Jamaican Black Castor Oil Strengthen & Restore Leave-In Conditioner — $14.00

For thick, thirsty hair, try this leave-in treatment from Shea Moisture. “This leave-in conditioner contains Jamaican black castor oil and shea butter that help to nourish and moisturize the hair as well as peppermint to stimulate the scalp,” Longsworth says. “It is definitely on the thick side but a little goes a long way.”

Klorane, Strengthening Serum with Quinine & Edelweiss — $32.00

Well+Good editors love this super serum by Klorane, which is fully loaded with nutrients your scalp will just slurp up. Between the heavy dose of vitamin Bs (B3, B5, B6, B7, B8), caffeine, manganese, and organic edelweiss, your scalp has everything it needs to start growing strong.

Ecoslay, Rice Pudding Leave-In Conditioner & Moisturizer — $21.00

This is like dessert for your hair and scalp. “This is a wonderful product with protein and healthy peppermint, rice water, and lots of herbal extracts,” says Dr. Longsworth. And it’s a multi-tasker, detangling and adding shiny while strengthening strands. 

Aveda, Nutriplenish Leave-in Conditioner — $34.00

Scroll through blog after blog of best leave-in treatments, and you’ll surely run into this pink Aveda bottle on some, if not all, of them. It’s beloved in the beauty community for its powerful formulation that protects strands and stimulates growth, all without weighing it down or knotting it up. It’s rich in key vitamins, antioxidants, and other expert-approved ingredients that will treat your tresses accordingly.

Bounce Curl, Moisture Balance Leave-In Conditioner — $24.00

“This leave-in conditioner is amazing, and it smells so good!” says Longsworth. “The ingredients are high quality and extremely moisturizing.” Just note, it doesn’t have any protein added in it, but makes a great primer for other products nonetheless.

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