“Brow serums help your existing brow hair take better root so you’re not shedding as frequently,” says Healy. They also help to prompt new growth and can even help fill in bald or sparse spots. Serums are “perfect for sparse, thinning, tail-less brows or those who over-plucked in the ’90s,” says Grande. However, Healy notes that these hairs may grow in lighter or thinner, so a good brow tinting can help amplify your new growth. Unfortunately, brow serums can not prompt new growth on areas with scar tissue.
King explains that non-prescription eyebrow growth serums are considered cosmetics by the FDA instead of drugs, which can directly promote hair growth claims. “With cosmetics, not much is permanent, and brands can only make ‘appearance’ claims,” she says. Zeichner agrees and adds that data shows that some peptides used in these formulas have biological effects on follicles—creating longer-lasting results.