A keratin SPA is a chemical process that smooths and shines frizzy hair. Results can last up to six months. There are many different versions of the treatment, and your hairstylist can customize a blend of the formula to suit your needs. Some versions of the treatment release formaldehyde when heated (more on that later), but many newer versions, like Manhattan hairstylist Arsen Gurgov’s proprietary “Rio” keratin treatment, are formaldehyde-free. No matter the formaldehyde content, on a basic level, keratin treatments dive into the hair follicle and inject porous areas with keratin, an essential hair protein. Your hair will appear healthier, because it actually is.