Hair may shed excessively if you don t have enough Iron in your diet, are generally malnourished or have a high thyroid hormone level. Your weight seems low (although I don t know your height) so I d recommend improving your diet to include plenty of fresh fruit and vegetables (especially green), lean meat, fish and whole cereals. You may do well to have a blood test to rule out the conditions I ve mentioned. Studies have also shown that overuse of hair coloring agents, straightening, and excessive brushing/combing/wearing hats can all lead to excessive hair loss. For dandruff, Shampoos containing Selenium tend to be the best place to start.