Hallo I Used Selsun Gold Once And My Hair Turned

hallo i used selsun gold once and my hair turned bright yellow. i was prescribed it by dermatoligist for a skinallergy contact dermatitis.. i am 71 and my white hair that i was avoiding putting chemicals on because of the skin condition.. has now been dyed grey and i hate it and it doesent cover the yellow anyway. i cant get help from selsun what can i do