Non-allergic hair dye is any hair coloring product that is made with natural ingredients rather than with common allergens such as hydrogen peroxide or ammonia. However, natural and organic products are not always hypoallergenic.
EcoColors and Corsval are two companies that provide hair coloring products made with natural ingredients, and L'Oreal offers an ammonia-free hair dye. Even with these types of products, it is still recommended that when trying new hair coloring products that a patch test is done to determine if the person is sensitive to that product. A patch test should be conducted by a hair care professional at a salon prior to getting the hair dyed.