That said, pollution’s precise toll on hair is unknown. “I haven’t seen a ton of research proving it’s a major threat,” says Schueller. “Of all the things that can harm hair — chemicals, brushing, heat — I’d imagine free radicals are low on the list.”
WHAT WORKS: With thinning and graying as potential consequences, why take chances? While only a diet rich in free radical-quelching antioxidants can truly defend hair at a follicular level, certain products and practices can help safeguard strands from the environment. For starters, “washing your hair thoroughly and with sufficient frequency for your hair type is key to curbing the scalp inflammation that contributes to hair loss,” says Dr. Henry. Shampoos with chelating agents, like EDTA, will gently extract heavy metals (found in car exhaust, cigarette smoke, and hard water).
You’ll also want to look for leave-ins with concentrated doses of antioxidants (think: vitamins, tea extracts, idebenone, resveratrol) to neutralize free radicals, and strand-coating silicones, proteins, and polymers, which “provide a physical barrier, walling off hair from pollutants,” says Hammer.
The Claim: Healing hydration
WHAT IT MEANS FOR HAIR: “With a rich blood supply and an abundance of oil glands, the scalp is an extension of our skin,” says Francesca Fusco, MD, assistant clinical professor of dermatology at New York City’s Icahn School of Medicine at Mount Sinai. It shares the same lipids and humectants, and it’s equally prone to dryness and irritation. Hair suffers from dehydration, too, particularly when its cuticle is eroded (by water, heat, and chemicals).
WHAT WORKS: Hyaluronic acid, a water-binding humectant, and ceramides, moisture-retaining lipids, are both found naturally in the skin (and in countless creams and serums). Since they improve the functioning of skin cells, making them more resilient and efficient, both can help keep the scalp in peak condition. When applied to hair (again, leave-on products work best), “they coat strands to lock in moisture while also shielding from heat and styling damage,” says Dr. Rogers, noting a 2002 study in which ceramides were shown to bind to African hair, helping to reduce breakage. Coconut oil and panthenol (a B vitamin) also nourish the scalp, and unlike most other ingredients, can penetrate inside the hair shaft, hydrating from within to enhance pliability, and keeping the cuticle tight and intact.
The Bottom Line
The secret to beautiful hair is a healthy scalp. “When the scalp is out of whack — meaning there’s poor circulation, an oil imbalance, or a build-up of cells — we see not only flakes and inflammation, but hair that looks and feels unhealthy, and may even shed before its time,” says Dr. Fusco.