The reasons can be : 1. Unhealthy life style (not eating properly, sleeping late, stress, lack of exercise) 2. Hormone induced hair fall which is called Androgenetic Alopecia 3. Low hemoglobin levels (but mostly seen in women) 4. Hypothyroidism (again mostly in women) 5. Chronic Telogen Effluvium 6. Hair straightening procedures 7. Dandruff . Whatever the reason you will need to visit a dermatologist and get yourself diagnosed.A treatment plan will be made for you and I'm sure you will benefit. Remember hair care is a process . There is no quick fix solution .