Hair Loss, Trauma, Cortizone Shots, Contact Dermatitis, Traumatic Alopecia. Treatment ?

Question : I had color and a haircut at a salon. When the hair dresser put a come through my thick, tangled, wavy, hair minutes after color treatment. He pulled so hard I felt like crying and the comb was full of hair a huge clump from my temples to the crown of my head. My head felt itchy during color and still after a month now. I have a blue vein right in the middle of the patch of hair loss 3 inches to 5 inches horizontally across my head. I am devasted. Visited primary dermo and they said hair loss due to truama and to get cortizone shots. I want a biopsy I want to know what damage there is? Also the dr gave me perscription .o1 fluocinolone acetonide topical solution. Question is can I have an accurate biopsy to determine cause, can I use the perscription without interferring with the biopsy results? What do I do in the future for grey hair shampoo I am 45 years old. No problem ever with hair loss actually I have so much hair and I can cover this awful huge spot by parting my hair. i want to know what happened so I do not do that again. Was the color left to long and my hair burned ? Did I have an allergic reaction after 2 years of the coloring at the same salon. Or the combination of hair damaged durling color and the hair dresser pulling it so hard at the spot the hair just came off on his come. XXXXXXX