Just like any haircare product applied to the scalp, we always recommend you take a close look at our ingredient lists and Sozo Hair Health Ingredient Glossary if you know you have sensitivities to certain ingredients. Our scalp and hair serum is designed to nourish and soothe your scalp; however, it is always best to start by applying a small amount or conduct a patch test before applying generously if you are concerned about your personal scalp sensitivities. It’s also helpful to know, that because our Scalp & Hair Health Serum does include rosemary oil, which is proven to stimulate blood circulation to help encourage hair growth, a small amount of tingling on your scalp is normal when using it as a pre-wash treatment.