InStyle

Hair

Our Editors Tested Dozens of Hair Growth Serums—These 13 Actually Worked

 

From thickening formulas to nourishing treatments, these top-tested oils and serums promote visibly healthier, fuller strands.

Hair health is a journey—one that naturally ebbs and flows over time. Age, stress levels, childbirth, medications, genetics, and even wearing certain hairstyles can affect the health of our strands and their growth (or lack thereof).

That’s where hair growth serums and oils come into play, helping offset thinning and shedding by creating—and, with regular use, maintaining—an optimal scalp environment from which happy, healthy strands will sprout and flourish. These concentrated blends are packed with nourishing ingredients and address a slew of common hair growth saboteurs. Generally, they are “designed to improve hair health by nourishing the scalp and hair follicles,” explains hair loss practitioner and certified trichologist Mandy Buechner. In doing so, “regular use of scalp serums and oils can lead to a healthier scalp and, by extension, healthier hair.”

Achieving healthy hair depends on the product type and its key ingredients. Rather than picking one and crossing your fingers, it pays to do your research—or better yet, read ours. To narrow down our top picks, InStyle editors tested a variety of the most beloved hair growth serums and oils over six weeks, evaluating each one on ease of use, formula consistency, and efficacy. We also spoke to two dermatologists, a trichologist, and a hairstylist for insight on what to consider when shopping.

The Winner
Augustinus Bader Hair Oil

Why We Love It: The brand’s proprietary, patented, research-backed and very beloved TFC8 technology is the hero ingredient in this serum-like hair oil, which is meant for application onto mid-lengths and ends only. Stacked on top of a base comprising argan, castor seed, pomegranate, and baobab oils, plus squalane and vitamin E, just two to three drops of this do-it-all oil instantly smooths, nourishes, detangles, and conditions strands. After consistent use, our tester’s straight, “sometimes stringy hair” was noticeably softer, shinier, and yes, longer.

Who It's For: Despite being a hair oil, its consistency is remarkably lightweight and not greasy; it absorbs easily and quickly into all hair types and textures, from thin to thick, straight to coily.

Size: 2oz | Key Ingredients: TFC8, vitamin E

Lauren, tester with thin, straight hair: “The most notable difference for me was in the shine, softness, and quality of my hair; using this oil consistently made my hair fuller and easier to style. The results were even better than I had anticipated.”

If You’re Looking for Minoxidil
Rogaine Women's 5% Minoxidil Foam

Why We Love It: Minoxidil, the active ingredient in this lightweight foam formula, is FDA-approved and clinically proven to help reactivate dormant hair follicles, effectively boosting regrowth in areas of thinning or loss. Ideal for women experiencing hereditary hair thinning, this quick-absorbing foam helps slow down hair loss and create a visibly thicker hairline with regular use—results can take three to six months, however, so patience is paramount.

Who It's For: Those seeking a reliable, no-nonsense solution for hair thinning and loss.

Size: 2.11oz | Key Ingredients: Minoxidil

Wendy, tester with fine, wavy hair: “I liked that it was so light and didn't really have any scent. My hair is pretty fine, but I never felt that the product weighed it down or made it feel dirty.”

If You Have Fine Hair
Briogeo Destined for Density MegaStrength+ Peptide Density Serum

Why We Love It: Formulated to promote stronger, thicker strands with prolonged use, this powerhouse serum is packed with peptides that strengthen hair follicles at the root, plus biotin to boost elasticity. It also contains a unique blend of caffeine, CoQ10 and ginseng, which work in tandem to nourish and invigorate the scalp, thereby supporting healthier hair growth.

Who It's For: Lightweight and fast-absorbing, this serum is ideal for those with thin or fine hair—unlike most oils, this formula won’t weigh down your strands. Anyone looking to enhance volume and improve hair density, regardless of hair type and texture, will benefit.

Size: 1.5oz | Key Ingredients: Copper peptides, biotin, caffeine

Katie, tester with straight, fine hair: “I was so impressed with the texture of this product—it did not leave any grease in my hair at all. After several weeks of use I'm starting to notice more fullness. I would say this serum is more intended for adding density and thickness rather than hair growth, although my hair does seem to be longer overall as well.”

If You Want Strength
Ceremonia Hair Oil & Scalp Massager Set

Why We Love It: Hair growth starts at the root, which is why this potent, plant-based blend is formulated to nourish and restore balance to the scalp. Key ingredients like meadowfoam and chia seed oils deeply hydrate, while castor oil and rosemary extract stimulate circulation. The formula also includes antioxidant-rich babassu, maracujá, and açaí oils, which protect against environmental stressors and prevent dryness. What’s more: it’s vegan, cruelty-free, and sustainably packaged.

Who It's For: Although it's particularly apropos for those with a dry or irritated scalp, all hair types will benefit from this lightweight yet deeply hydrating oil. Those with long strands will particularly enjoy its ability to boost both hydration and strength.

Size: 2oz | Key Ingredients: Castor oil, rosemary extract, meadowfoam seed oil

Stella, tester with straight, fine strands: “My hair feels much more hydrated, healthy and full. I am very prone to split ends and I also have long hair that hits my belly button, so the ends get dry quickly—but I haven't noticed any significant dryness on the tips of my hair [while using this product].”

If You Want New Growth
Evolis Professional Promote Activator

Why We Love It: A powerful blend of hair and skin boosting botanicals, the hero ingredient in this targeted serum is a plant extract called sanguisorba officinalis, which stimulates and soothes the scalp, increases circulation, and helps balance oil production—all of which support faster, more robust hair growth. By boosting blood flow and helping offset a host of factors that can impede hair growth (such as irritation and dryness), this serum supports an ideal scalp environment for healthy strands to grow and thrive.

Who It's For: Those experiencing thinning or early stage hair loss will reap the most benefit, though anyone wanting to stave off hair shedding and boost overall vitality will appreciate this potent (yet lightweight) serum.

Size: 2oz | Key Ingredients: Sanguisorba officinalis, rosemary oil, green tea extract, vitamin E

David, tester with coarse, fine hair: “After three weeks, the product left my follicles more activated, my hair thicker, and as a result my scalp felt more abundant with hair than normal. I noticed my hair looking less sparse and darker in certain areas.”

If You Want Thickness
Kérastase Scalp & Hair Serum

Why We Love It: Designed to improve hair texture from root to tip, this targeted serum works to stimulate the scalp, strengthen follicles, nourish roots and smooth frizz—in sum, making strands thicker and more uniform. The formula’s native plant cells (including a key ingredient derived from apple stem cells) helps rejuvenate hair follicles to encourage denser growth, while green tea extract provides antioxidant protection.

Who It's For: With a host of ingredients that help strengthen hair from the roots through the lengths and ends, this universally appealing serum is perfect for anyone wanting to boost thickness, as well as those seeking a two-in-one solution for both scalp and hair care.

Size: 2oz | Key Ingredients: Gluco peptide, native plant cells, fruit cell culture extract

Paden, tester with fine, thin hair: “I noticed considerable hair growth as well as added thickness. It definitely feels like my hair has grown faster and I am due for a haircut sooner than I thought.”

If You Have Curly or Coily Hair
Pattern Argan Oil Hair Serum

Why We Love It: Like a spa day for your curls in a bottle, this nourishing, antioxidant-packed cocktail of argan, sunflower, castor, sweet almond, and shea oils is specifically formulated to hydrate, strengthen and soften curls without weighing them down. While it’s perfect for curly strands that need some extra frizz-fighting love, it also doubles as a pre-shampoo scalp treatment for dry, irritated skin. Pro tip: A little goes a very long way.

Who It's For: While it’s perfect for curly strands that need some extra frizz-fighting love, it also doubles as a pre-shampoo scalp treatment for dry, irritated scalps.

Size: 3.5oz | Key Ingredients: Argan oil, castor oil, sunflower oil

Sidney, tester with thick, curly hair: “My hair feels softer and looks healthier after using the product; It appears shiny and full, [and] my hair and scalp did not feel greasy after use.”

If You Want Fullness
Viviscal Hair Thickening Serum

Why We Love It: This volume-boosting miracle in a bottle is packed with ingredients that promote thicker strands from mid-lengths to ends, including biotin, keratin, marine collagen and seaweed extract. A pump or two of this thin, water-like leave-in serum is all you need to achieve visibly thicker-looking strands (this product isn’t intended to promote growth—or be applied onto the scalp at all).

Who It's For: Anyone looking for an instant volume boost. Those with fine or thin strands will appreciate its ultra-lightweight texture.

Size: 1.69oz | Key Ingredients: Biotin, keratin, marine collagen

Ciara, tester with fine, straight hair: “​​I think this product does a good job of giving immediate volume. It’s virtually weightless, which is nice because it didn't weigh down my hair at all.

If You Want Healthier Hair
Adwoa Baomint Protect & Shine Oil Blend

Why We Love It: Formulated with a blend of 15 different natural oils, including argan oil, peppermint, coconut and baobab, this scalp oil’s ultra-nourishing, nonirritating formula noticeably improved our tester’s hair texture and appearance. A targeted applicator tip “makes it easy to apply the oil directly on the roots of the hair, while the squeezable bottle ensures you can use all the product and nothing will be left behind,” said Michal, our tester.

Who It's For: Anyone seeking to improve overall hair health, although its thick consistency renders this oil an ideal choice for dry, curly or coily strands.

Size: 2oz | Key Ingredients: Baobab oil, argan oil, peppermint oil

Michal, tester with wavy, color-treated hair: “I saw overall improvement in my hair texture and appearance; my hair felt and looked softer, shinier, and healthier. I had no irritation or tingling feeling, even though I used a generous amount multiple times a week.”

If You Want Moisture
Bomba Curls Dominican Forbidden Oil

Why We Love It: This all-natural blend of coffee seed, castor and black cumin seed oils, plus rosemary extract to help stimulate new growth, is chock full of beneficial antioxidants and fatty acids. It’s also multipurpose: use it as a soothing scalp treatment to nourish hair follicles and promote growth, or apply it onto lengths and ends to lock in moisture and boost shine. Regardless, a little goes a very long way.

Who It's For: It’s best suited for those with thick or overly-parched strands; thin or fine-hair types will find this oil blend too heavy.

Size: 4oz | Key Ingredients: Coffee seed oil, castor oil, rosemary extract

Martha tester with curly, formerly thick strands: “I have seen positive effects from using this product: richer color, added softness, and less frizz. It (also) smells great, is a lovely addition to my hair regime, and is inexpensive for the quality and amount.”

If You Want a Lightweight Oil
K18 Molecular Repair Hair Oil

Why We Love It: This ultra-lightweight hair treatment—which you’ve undoubtedly seen touted by celebrities on social media—combines cutting-edge science with high-performing ingredients. The result: it repairs damage on a molecular level. More specifically, the brand’s patented bioactive K18 Peptide penetrates deep into the hair cortex to repair and regenerate damaged keratin, thereby improving strength, elasticity, and smoothness. Moreover, nourishing ingredients like jojoba oil, vitamin E, and squalane deeply hydrate, enhance shine, and protect against environmental stressors.

Who It's For: Ideal for anyone with dry, damaged, or chemically treated hair, though all hair types and textures will benefit from its ability to repair breakage and boost overall hair health.

Size: 2oz | Key Ingredients: Peptides, jojoba oil, vitamin E, squalane

Aliyah, tester with thick, curly hair: “This product did come through on its promises: my hair was visibly shinier and had less frizz after incorporating the oil into my regular hair care routine. The product didn't make my hair look or feel greasy—it was very lightweight.”

If You Want Less Fallout
Philip Kingsley Density Preserving Scalp Drops

Why We Love It: This science-backed solution contains a unique peptide blend that simultaneously helps slow hair shedding and improve density. Combined with caffeine to boost blood flow and saw palmetto, which works to block DHT (the hormone linked to hair loss), these easy-to-apply scalp drops work steadily over time to strengthen and maintain the hair you already have and also encourage new growth.

Who It's For: Anyone wanting to improve hair density and/or tackle thinning with one convenient, easy-to-use product. Our tester reported surprisingly fast hair growth results, sans any strong fragrance or leftover residue after application.

Size: 287oz | Key Ingredients: Biomimetic peptide blend, saw palmetto, caffeine

Laura, tester with thin, straight hair: “After using the product for a while, my scalp was sprouting a lot of tiny new-growth hairs and I didn't see as many hairs in my hair brush. Less fall out meant that my hair was actually gaining some more depth to it!”

If You’re Looking for Castor Oil
Wild Growth Hair Oil

Why We Love It: This tried-and-true hair growth elixir contains a concentrated blend of plant and essential oils—including coconut, jojoba, and olive oils—which work in tandem to hydrate the scalp and in turn, promote healthy new growth. Use it as a hot oil treatment before shampooing or apply a few drops onto mid-lengths and ends as needed to detangle, soften and boost shine.

Who It's For: This universally beloved hair oil does it all—hydrates, detangles, softens, boosts shine and promotes growth—for only $10, no less.

Size: 4oz | Key Ingredients: Castor oil, coconut oil, jojoba oil

Chantia, tester with thick, 4C curls: “This product did give me the desired growth as well as fullness I was looking for, specifically when it came to my edges. I loved the easy application and how well it works with protective styles.”

Our Testing Process

There are hundreds of different hair loss-correcting products available, but knowing which ones will deliver results is the hardest part. So InStyle editors and our testing partners did the trial-and-error so you can choose a product that you know works. We tested several dozen hair growth oils and serums for six weeks taking note of the application process, texture, how our hair looked and felt after applying, and of course, the growth or results. The ones we made winners were successful in all categories and got rave reviews from our testers.

What to Keep in Mind

• Your Type of Hair Loss: There are many causes of hair loss, ranging from lifestyle factors like stress and wearing tight hairstyles, to age and postpartum, or more serious medical issues, such as vitamin deficiencies, thyroid issues and taking certain medications. If yours falls into the latter category, hair oils and scalp serums likely won’t suffice—the underlying condition must be treated first. Bottom line: If you experience hair loss that is sudden and/or significant (i.e. consistent clumps of hair), always consult with your doctor.
• Your Hair Type: Those with fine or thin hair and oily-scalp tendencies should avoid heavier hair oils and instead opt for a lightweight serum, which won’t weigh down strands or exacerbate excess sebum. For those with brittle, dry, thick or textured hair, oil-centric products will lock in much-needed moisture.

Your Questions, Answered

How do hair growth oils and serums work?

“Depending on the product, there may be ingredients that help with hydration, serve as antioxidants, decrease inflammation of the scalp, and rebalance pH,” explains board-certified dermatologist Gloria Lin, of Schweiger Dermatology in New York City. Additionally, some scalp oils and serums help maintain the scalp’s microbiome and support protein synthesis, the process inside the hair follicle that promotes hair growth,” says Sandra Petrut, professional hairstylist at Maxine Salon in Chicago.

Which over-the-counter active ingredients are the most effective for hair growth?

There are a variety of effective, OTC active ingredients for promoting hair growth—here are the most common:

• Minoxidil: “This is the gold standard for over the counter hair loss treatment,” says Dr. Lin. “Minoxidil may help increase circulation to the scalp and improve oxygen and nutrient delivery that can promote hair growth. It may also increase the number of hair follicles in the anagen, or active growth phase.”
• Jojoba Oil: “Formulas with jojoba oil can help stimulate blood to circulate in the scalp, which can promote hair growth,” says board-certified dermatologist Howard Sobel, M.D. 
• Vitamin E: Rich in fatty acids that nourish follicles, this antioxidant also helps fight off free radicals to protect the hair and scalp against damage.
• Biotin: “Also known as vitamin B7, biotin supports hair strength and growth,” explains Buechner. “It also helps to improve the infrastructure of keratin, a protein crucial for hair health.”
• Caffeine: “More studies need to be done to determine the mechanism of action and effectiveness of caffeine as an ingredient, [but it] may increase blood flow or circulation of oxygen and other nutrients to the hair follicles,” explains Dr. Lin. “Caffeine also contains flavonoids, which can serve as an antioxidant to help protect the hair and scalp from damage 
• Rosemary Oil: This natural ingredient has a host of hair benefits: it stimulates follicles, promotes new growth and an optimal scalp environment, protects against oxidative damage, boosts blood flow, strengthens strands and contributes to overall healthier hair. 
• Castor Oil: “The main benefits of castor oil are smoother strands, preventing split ends, promoting scalp health by being antibacterial and anti-inflammatory,” says Petrut.

Which ingredients should I avoid? 

Regardless of hair type or texture, always try to “avoid solutions or gels that clog your pores,” Dr. Sobel advises. “I also recommend avoiding products with sodium sulfate and mineral oil because they clog pores, and silicone, as it can be difficult to absorb.”

How long does it take to see results? 

"Hair loss treatments typically require at least six months to see results, so consistency is important,” explains Dr. Lin. That said, for most products you can see visible results in six weeks.

Why Shop With Us

Rebecca Dancer is a beauty writer, editor, and consultant with nearly 15 years of experience in the industry. Curious to a fault, her childhood nickname was "Talkie" because she asked so many questions—a trait she has yet to outgrow, especially as it pertains to skin care ingredients.

For this story, she worked with board-certified dermatologists Dr. Gloria Lin and Dr. Howard Sobel; trichologist Mandy Buechner; and hairstylist Sandra Petrut to get their expert insight on what makes for the best hair growth oils and serums. Each product on this list was thoroughly tested and reviewed by InStyle editors and our testers.