Nécessaire The Scalp Serum ($58)

For those experiencing thinning hair or hair loss, or a dry, irritated scalp, this daily scalp treatment is a must-try. The watery, oil-free serum is made with a 5-percent biomimetic peptide blend of five peptides at concentrations that have been clinically proven to help visibly minimize thinning and support new hair growth, as well as seven different molecular weights of hyaluronic acid for a mega boost of hydration. Green tea extract helps soothe itchiness, too, and if you’ve ever experienced an itchy scalp, you know it’s the worst!

There’s also no alcohol, silicones or synthetic fragrance in the ingredient lineup, and it’s safe for color-treated and keratin-treated hair. If you use it every day as suggested, one bottle should last you two months: Just part your hair into sections and apply the dropper directly on your scalp and then massage it in.

In a clinical perception study (participants also used the brands shampoo and conditioner), 80 percent of people said their hair looked thicker, 84 percent said their hair looked fuller and 88 percent said their hair looked healthier.