Feeling Bad About … Your Hair?

“We know that the fiber curvature of hair changes and gets less regular as we get older, but we don’t know exactly why that happens — just that it happens,” said Dr. Thomas, who is also a principal scientist behind Hair Biology.

John Barrett, a hairstylist who tends to Martha Stewart’s and Hillary Clinton’s trademark cuts in his Manhattan salon, advises clients to wash their hair no more than twice a week with gentle shampoo and to sleep in hydrating hair masks to improve manageability and shine. His mantra: Do less.

“Most hair problems are self-inflicted,” Mr. Barrett said.

What about shampoos, supplements and serums? Do those things actually work?

They can, but choose wisely. Most specialty shampoos and serums, like the Scalp Stimulating Booster from Curlsmith, a hair-care line headquartered in Britain, work by helping to improve blood flow to follicles. (Curlsmith’s serum includes ginger and guarana, which have been shown to improve circulation, said Afope Atoyebi, a trichologist in London who has consulted for the company.

Dr. Linkov underscored that the only topical solution with significant medical research behind it is minoxidil, sold under the brand name Rogaine, which works by dilating blood vessels and may extend hair’s growth phase. Some doctors are also prescribing topical finasteride, traditionally taken as a pill and better known by the brand name Propecia, which blocks testosterone from converting to DHT, an androgen (male sex hormone) that is linked to thinning hair in both men and women.

Finasteride should not be taken by women who are pregnant or could become pregnant. Dr. Schwartz prescribes a compound serum made of finasteride, minoxidil and biotin to patients who are not going to become pregnant.

Supplements, likewise, can be helpful. Nutrafol, for example, makes a supplement that uses maca powder, saw palmetto and other ingredients to combat hair loss related to hormonal changes in perimenopause and menopause. Phase 1 of the company’s clinical trial of the supplement was recently published in the Journal of Drugs in Dermatology.