How it works: The ultra-concentrated formula, with Co Zyme-10 Vitamin Complex, targets areas of advanced thin-looking hair such as the hairline or crown. Keratin helps protect against cuticle damage & boost fragile hair. Directions for use: - Designed to complement your NIOXIN 3-Part System, Nioxin Hair Booster is used twice daily: in the morning before your Scalp Treatment & again in the evening. - Its vitamin-enriched formula will give a temporary redness to skin after application.