I had excessive hair shedding after substantial, rapid weight loss. I was also diagnosed with B12 deficiency. So not sure of exact cause, even after extensive blood work. (Hopefully, it will resolve on its own, but I can’t be sure so sought help.) I discussed it with my dermatologist and she prescribed Minoxidil. I take it in pill form. I also began Vitamin B12 treatment. She says the only fda approved treatments for hair loss are Minoxidil and Finasteride. I use a shampoo with biotin that I like. I am no longer shedding excessively, but I don’t think it’s due to the shampoo,