Yes it can be used by those who are allergic to other hair colors & have sensitive skin.
Yes, It is 100% safe, because of NO PPD, NO Ammonia and No Peroxide. It is the brand of Vegetal (AMA Herbal) which is PPD free hair color manufacturer, and its product recommended by Dermatologist as well.
No, its Gluten free product.
It is 100% safe to use but as precautionary we write for patch test before you apply on hair because some of people also allergic from natural ingredients like coffee