Hair loss after bariatric surgery has everything to do with the anesthesia and the surgery. We have depleted our bodies of so much at the beginning and put so many foreign chemicals that after surgery you hair and nails pay the price. The keratin straighter s are not to harmful so try it out, also Keratin is more restorative than damaging but remember in coloring or straighten we are opening and closing the cuticle of your hair so that always no matter what causes a little damage. I am a stylist and 4 weeks out of surgery and today was the first time I noticed a large amount of hair and I can tell you it is because I have been so sick and not getting my protein The main important things are protein, a shampoo like Nixon to get the scalp and follicles cleansed, water and vitamins. Everything is trail and error if you notice your hair isn't handling it the same I would stop.