Allergy after hair dyeing occurs when the ingredients contained in the hair dye cause allergy to occur on the scalp and surrounding facial skin that is in contact with the hair dye. The most effective treatment after allergy is intravenous hormone medication such as methylprednisolone, and can also be treated with calcium, vitamin C or intramuscular injection of compound betamethasone injection, together with oral anti-allergy medication such as loratadine tablets. If a local rash is found to be allergic and there is exudate, it can be cleaned with saline, wet compresses, and topical mupirocin ointment to prevent secondary infection. When there is no exudation, topical hormonal ointment, such as hydrocortisone ointment and mometasone furoate cream, can be used. If the allergy is severe, minimize the irritation of the hair dye on the hair and cut the hair, which also facilitates the use of medication. Recovery from allergies after hair dyeing takes at least a week or so, and care should be taken not to use the same ingredients of creams when dyeing hair again. Whether it is a chemical hair dye or a plant hair dye, apply it to your arm for a period of time before using it to observe whether it is suitable.