The Nioxin System 4 Scalp and Hair Shampoo is on sale. It strengthens fine, thin, aging hair and promotes new hair growth in as little as 30 days. Amazon shoppers are impressed by the formula, which Alyssa Milano attributes to fuller hair.

Others "cannot believe" how much volume it gives hair.

When considering physical changes associated with aging, skin-related concerns may be the first to come to mind. However, changes in hair color and density can be just as notable—if not more so—for people who experience the natural shedding and hair loss that can come with aging. If you’re among the many people whose mane is thinning, perhaps you’re frustratingly familiar with the search for a solution that actually works. Nioxin—a brand Alyssa Milano has attributed to her hair regrowth after COVID-19-triggered shedding—offers science-backed hair growth solutions. 

Its System 4 Scalp and Hair Shampoo has thousands of five-star ratings, with many reviewers who echo Milano’s sentiments. The formula is on sale at Amazon, where it’s marked down to $25.  

Nioxin System 4 Scalp and Hair Shampoo

Orig. $47 $25 at Amazon

The Nioxin System 4 Scalp and Hair Shampoo is a strand-strengthening, scalp-nourishing treatment for fine, limp, damaged, and thinning hair that’s even safe to use on color-treated tresses. In addition to improving the health of existing strands, the shampoo promotes new growth, with the brand saying you may see visible results in as little as 30 days.

While seemingly lofty, this claim checks out with happy reviewers. Shoppers report impressive results, and the formula’s nutritive, science-backed list of ingredients explains why. Caffeine, for instance, wakes up follicles by increasing healthy circulation to the scalp. Similarly, peppermint oil, a natural root-stimulator, has been shown to “increase dermal thickness [of the scalp], follicle number, and follicle depth,” dermatologist Dr. Marisa Garshik, M.D., previously told InStyle. Similarly impressive? “In lab studies, peppermint oil has comparable effects to Rogaine,” dermatologist Dr. Shirley Chi, M.D., added. 

Because a healthy head of hair begins with a healthy scalp, the shampoo contains ingredients commonly found in skincare, including niacinamide. A form of vitamin B, the ingredient has amassed ample buzz from dermatologists for an array of reasons, including its anti-inflammatory, soothing properties. Niacinamide has “a similar effect on the scalp skin” as it does on the face, dermatologist Dr. Branden Camp, M.D., previously told InStyle. It can “address irritated, sensitive scalps” to create a healthier environment for follicle growth. 

Shopper acclaim for the shampoo is vast, with more than 3,000 five-star ratings at Amazon and numerous self-proclaimed loyalists. One 80-year-old shopper said the shampoo has “put a stop” to their hair loss. Another reviewer, who is in their 60s, said they “cannot believe” the volume they’ve gained from the “wonder” formula. Another fan with “baby-fine hair” reported a “very noticeable difference” in thickness as a result of using the shampoo. 

For stronger, fuller, hair and noticeable new growth in as little as one month, shop Nioxin’s System 4 Scalp and Hair Shampoo on sale—plus more fortifying solutions, below.

Nutrafol Shampoo

Orig. $44 $42 at Amazon

Maple Holistics Rosemary and Biotin Shampoo

Orig. $14 $12 at Amazon

Pura D'or Anti-Thinning Biotin Shampoo

$30 at Amazon