If we’ve learned anything from our abundant coverage on managing hair thinning and maximizing growth, it’s that no one product or regimen is completely foolproof. But if we were going to get as close as possible to solving the problem of hair loss, what would be the one ingredient (or ingredients) to look for? “When it comes to hair growth products, the key clinically proven ingredient that people should look for is topical minoxidil,” said New York City-based trichologist Sophia Emmanuel. You’ve likely heard of this FDA-approved ingredient that is used to treat common conditions like pattern hair loss, and that is the active component in over-the-counter products like Rogaine. Emmanuel explained that minoxidil works by increasing blood flow to hair follicles, which extends the hair growth phase.“It [also] helps to enlarge hair follicles that miniturize, which can produce longer and thicker hair strands,” she said. Board-certified dermatologist and hair restoration expert at Golden State Dermatology Dr. Paul Rose said that minoxidil is offered by brands other than Rogaine, and if you’re comparing two products contain the same percentage of minoxidil, they usually work just as well regardless of price.Another factor that might affect the cost? “In some cases, the solution the minoxidil is dissolved in may be different, which can affect how well people tolerate the product,” said Rose. “Products can also vary in their formulations or ingredients.”Granted, not everyone wants to use minoxidil, nor will it have the same effectiveness for every person and type of hair loss.“It is important to know the type of hair loss you have to learn the best form of therapy before purchasing products over the counter,” Emmanuel said. (You can read more about different causes of hair loss in our previous coverage or by consulting a physician.)But, if you want to see some of the market options out there that contain this trusted ingredient, take a look at some of them below. Plus, learn about a few other ingredients (and the products that contain them) that professionals say may also impact hair growth.It’s important to note that 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. The experts consulted for this story do not necessarily endorse the products ahead unless otherwise noted.AmazonA tried and true minoxidil foam by Rogaine"In general, I often recommend starting with a well-known brand like Rogaine," Rose suggested. As we mentioned earlier, Rogaine is probably the best-known product that features minoxidil as the active ingredient for hair growth.This three-month supply features a 5% minoxidil along with a variety of botanical extracts and humectants, which can draw moisture into the hair. Rose also spoke about whether you really need to follow the "for men" or "for women" designation on minoxidil formulas and why the latter is typically only found in 2% concentrations: "The 2% was originally tested in women, and the 5% was only approved for men by the FDA.”The once-a-day treatment is also in the form of a foam, an important requirement according to experts like board-certified dermatologist Dr. Brendan Camp, so the product won't drip down to other areas of the face, thus risking unwanted hair growth.AmazonA highly rated Amazon-brand minoxidil treatment "Many brand-name and generic products contain minoxidil, including pharmacy store brands and online formulas," Rose said. If you don't want to pay big box prices, we found this Amazon-branded minoxidil treatment, which has been rated by nearly 8,000 shoppers and has up to 4.2 stars. Available in both 2% and 5% concentrations for women and men, respectively, this treatment comes in an unscented liquid that's easily dispersed with a dropper. AmazonAn extra-strength treatment spray with minoxidil Emmanuel suggested the minoxidil formulations from Bosley MD, a hair care brand with tons of products aimed at combatting hair thinning. This particular hair growth treatment, available for both men (5%) and women (2%), comes in a no-mess spray formula that's unscented and easy to apply. Each bottle contains a one-month supply of treatment. TargetA regrowth serum with 5% or 2% minoxidil for men and womenEmmanuel also said that the online wellness platform Hims & Hers offers regrowth treatments containing minoxidil at affordable prices. These unscented regrowth serums, available in formulas for both men (5%) and women (2%), apply with a precision dropper.You've also probably noticed by now that minoxidil treatments marketed to women tend to come in the lower 2% concentrations — however, Hers offers a minoxidil foam for women with 5% of the active ingredient.The brand offers even higher concentrations of minoxidil treatments that are not available over-the-counter, but which you can have prescribed and mailed directly to your door, without ever having to leave your house.AmazonA thickening shampoo and conditioner fortified with peptides and biotin"Combining minoxidil with a strengthening shampoo and conditioner can help your hair look fuller," Emmanuel said. According to her, the V&Co Thicker Please shampoo and conditioner is formulated with peptides, which, she said, can help support hair follicles, scalp circulation, and increased density.AmazonA peptide-packed density serum from The OrdinaryBased on Emmanuel's guidance that peptides may help support hair growth, especially when used in conjunction with minoxidil, we selected this popular hair density serum by The Ordinary, which features a concentrated dose of multiple peptides. This lightweight leave-in serum also contains a buffet of plant extracts that help nourish the scalp for healthier-looking and feeling hair over time. AmazonA DHT-blocking shampoo"Dihydrotestosterone (DHT) is a hormone thought to be responsible for hair shrinkage and loss," Camp previously said. "This shampoo is formulated with saw palmetto, a botanical ingredient that is thought to inhibit the activity of DHT and promote hair growth."Endorsed by the American Hair Loss Association, this clinically developed shampoo claims to target three different zones of hair loss, including those from inflammatory and nutritional causes.AmazonAnother DHT-blocking shampoo with biotin and pumpkin seed oilThe Pura Dor shampoo is an additional DHT-blocking option that's been well-received among its users. It's an aloe vera-based formula containing saw palmetto, nourishing argan oil and tons of other hair-loving ingredients. It also features the inclusion of pumpkin seed oil, an ingredient that dermatologists have previously said might be helpful for some people experiencing hair thinning.