The experts consulted for this story do not necessarily endorse the products ahead unless otherwise noted.Finding the right products on your hair loss journey can involve some trial and error, especially when it comes to figuring out which ingredients really work for you. (Do you use minoxidil? Opt for something else? What about your shampoo?) However, there’s one helpful ingredient for thinning hair you may not have thought of yet — and you might already be using it in your skin care.In a previous story about the best shampoos for hair loss, Dr. Dendy Engelman, a board-certified dermatologist at Shafer Clinic Fifth Avenue in New York City, mentioned that peptides are a good ingredient for supporting the scalp and reducing shedding. Peptides are a common ingredient in anti-aging skin care these days — according to previous HuffPost reporting, they can help with collagen production and smooth wrinkles and fine lines on the skin.I followed up with Engelman to ask about the science behind peptides and their potential impact on hair loss.“Peptides are short chains of amino acids that act as signaling molecules in the body, essentially ‘telling’ cells how to function,” Engelman said. “When it comes to hair health, certain peptides can help support the hair growth cycle by promoting a healthier scalp environment, improving follicle function, and potentially extending the anagen — or growth — phase of the hair cycle. Some peptides are also believed to increase blood flow to the scalp and reduce inflammation, both of which are key factors in maintaining strong, resilient hair.”Other experts who previously spoke to HuffPost also mentioned this useful function of peptides: Trichologist Sophia Emmanuel said peptides can help increase density by supporting hair follicles and scalp circulation in a story about the best products for hair loss. And in speaking about the viral Cécred Hair & Edge Restoring Drops, which also contain peptides, board-certified dermatologist Dr. Dina Strachan explained that different types of peptides have different benefits, including the increased blood flow and extension of the growth phase mentioned by Engelman.Armed with Engelman’s insights, we’ve got our eyes on this multi-peptide serum for hair density by the Ordinary, which reviewers call “magic in a bottle.”Engelman has no association with this editor’s pick, but here’s why it caught our attention: The “game-changer” serum uses multiple kinds of peptide technology to help support the scalp and make hair appear thicker, fuller and denser. It also contains nourishing plant extracts to maintain a healthy scalp.The serum is fragrance-free and sulfate-free (derms have previously warned against using sulfates if you’re concerned about hair loss, because they can strip the scalp of natural oils, leading to dryness and inflammation). It’s also so easy to use as a lightweight, water-based leave-in serum: Just apply a few drops to your clean, dry scalp once a day (the brand recommends at bedtime).AmazonThe leave-in serum is water-based and chock-full of peptides to help support the scalp for thicker, fuller-looking hair.Reviewers are amazed at how much the serum has helped their thinning hair. “I’m 40 with fine, thin hair that I have damaged with bleach. I have some hair loss at the corners of my hairline, like mini bald patches, and I had noticed a lot of hair falling out in the shower and on my brush,” wrote one reviewer, who said they have a family history of hair loss and now use the serum along with a dermaroller. “I have almost no shedding in the shower now! I even bleached and colored my hair and had very little fallout. I am noticing hair growing back along my hairline and in the balding spots. My mom, who sees me every day, even commented that my hair looks thicker.”Others call the results “mind blowing” and have shared before and after pictures with visible growth in just about a month of use. “[Y]’all… let me put you on this,” one enthusiastic shopper gushed. “I have been using it every night on my hairline for months now and [I] have a TON of new baby hairs!!! It’s not greasy at all, no smell as far as [I] can tell, dries quickly, doesn’t irritate my sensitive skin and scalp, and of course WORKS!!!!”In addition to the gentle formula and effectiveness with consistent use, the under-$25 price tag is also a bonus. As one reviewer put it, “You definitely have to be consistent and patient with it — it’s not an overnight miracle — but it’s affordable compared to a lot of other hair serums out there.”Just remember: Peptides are a great supplement, but they can’t do it all on their own.“While peptide-infused topicals can be a helpful part of a hair care routine — especially for early thinning or maintenance — they are generally more supportive than transformative on their own,” Engelman advised. “In-office treatments like platelet-rich plasma (PRP), which uses your body’s own growth factors to stimulate the follicles, tend to deliver more significant results for patients experiencing more advanced hair loss. Ideally, I view peptides as a complementary approach: they can help optimize scalp health and enhance results when used alongside clinically proven treatments like PRP.”If you’re concerned about thinning hair, peptides can be a more affordable addition to your hair care routine. Shoppers certainly seem to agree: Below, find some more promising reviews from users who have put the Ordinary serum to the test on their own hair.“When I lost a bunch of weight, I lost a bunch of hair too. To help remedy this problem I tried so many different things. Some products didn’t work, some left my hair feeling oily, sticky or crunchy and another one that really worked was $150 per month which was unsustainable. The reviews on this product were good so I gave it a try along with a rubber type brush to stimulate blood flow and spread the product. I have been using it for two months now and yesterday someone actually told me that I have thick hair! This product contains effective ingredients, it is not sticky or oily and most importantly it works really well at helping to thicken and regrow lost hair. It comes with a dropper and it is a clear liquid. No strong smell and easy to distribute on the scalp with no irritation. Not only does it work but it has an excellent price point. I will continue to use this hair product and I very highly recommend.” — sailfishes“Seriously my new holy grail. I got off birth control and my hair literally started falling out. Started using this product and I couldn’t believe the growth I was seeing around my hair line. My hair stylist even made a remark how she noticed all the new growth. I have fine hair and it didn’t make my hair that greasy. I started seeing noticeable results after about a month of use!” — Katlin Pacheco“For years I’ve tried to grow my hair but nothing has worked as quick as this product. I’ve been using it for over 2 years and my hair has become fuller. I use it every wash day and put it before bed. It’s non-greasy and very light weight serum. I have so much baby hair now and it takes longer to get my hair done now that I have more hair. It’s a miracle worker.” — Karina Rodriguez“I started using this product religiously after I lost all of my hair due to chemotherapy. While I don’t think it necessarily has made my hair grow faster, I think it has TRANSFORMED the health of my scalp. I use this after every shower and I never get dry flakes, dandruff, or oily scalp anymore. If anything, I think it has made my regrown hair so much healthier since my scalp is so balanced! I am on my 3rd bottle of this magic potion. Please never stop making this!!!” — SierraCheck out a few more over-the-counter hair products for thinning hair, rounded by HuffPost senior shopping writer Tessa Flores:AmazonA classic minoxidil treatmentBoth New York City-based and board-certified dermatologists Dr. Brendan Camp and Dr. Blair Murphy-Rose had Rogaine at the tops of their lists of goods with hair-growing potential. "Minoxidil is the active ingredient in Rogaine and it is thought that minoxidil helps hair remain in the growing phase of its growth cycle," Camp explained of this well-known treatment, available in formulas for both men and women. It features a 5% concentration of this active ingredient along with a variety of botanical extracts and humectants which can draw moisture into the hair. The once-a-day treatment is also in the form of a foam, an important requirement according to Camp so the product won't drip down to other areas of the face, thus risking unwanted hair growth.Minoxidil belongs to a class of drugs known as vasodilators, so be sure to read the list of side effects and speak to your doctor before using.AmazonA widely endorsed ketoconazole shampooExperts regularly sing the praises of the reviewer-beloved Nizoral shampoo, a "gold-standard" of dandruff treatments, according to one dermatologist."The active ingredient in this dandruff shampoo is [1%] ketoconazole, which has antifungal properties," Camp explained. And although he admits that evidence is limited, ketoconazole may help to reduce inflammation and the hormonal influences that can contribute to hair loss in addition to helping to alleviate dandruff. And if you're traumatized by other medicated anti-dandruff shampoos in the past, reviewers assure us that, unlike other market options that smell unpleasant, are harsh on hair and can have it feeling dry and gunky, Nizoral leaves tresses soft and clean-smelling.AmazonA rosemary hair strengthening oilCamp and Murphy-Rose mentioned that the inclusion of rosemary oil in your hair care routine may prove to be beneficial for managing excessive shedding. This is because "rosemary oil is a source of carnosic acid that is thought to help reduce inflammation and stimulate hair growth," according to Camp.In line with that advice, we thought it would be worthwhile to include the viral Mielle oil, a rosemary mint scalp and hair strengthening treatment that has become TikTok-famous for its anecdotal claims surrounding improved hair health and growth. (It’s Amazon’s second-best seller in the beauty and personal care category.) The biotin-infused formula contains nutrient oils including jojoba, grape seed and evening primrose, all of which can address dryness and brittle-feeling hair along with other scalp health factors that can affect hair retention.