Always do a patch test to see how your skin reacts before using a new hair product. If it stings or itches, try a different brand. If you're coloring your hair, try a semi-permanent color or a rinse. Permanent color has an ingredient called PPDA that can cause an allergic reaction. To limit exposure to harsh chemicals, retouch the roots instead of doing all-over color every time. Or highlight instead of lightening all over.