Greetings! Avoid using hair colour / if you have to use hair colour - try using vegetable derived hair dyes - these are not very strong or do not give very dark colour - but fewer chances of these streaks and pigmented cosmetic dermatitis with them. See a qualified deramtologist - if there's any pigmented cosmetic dermatitis - TCS based creams/ with or without immunomodulators should help. Then creams for reducing the pigmentation can be added. Hope this helps; warm regards. Dr Govind Suresh Mittal. Bengaluru