Well alopecia is just hair loss, could be a range of reasons;
Diet/alcohol
Genetics
Stress
Diseases
Lifestyle
Too much styling products/chemicals
Ironing your hair too much lol
Restricting blood flow
Wearing a hat or somekind of headwear to tight.
Anabolics
Supplements
Best way is to speak to a specialist and see whats going on, in the mean time you can get some hair loss shampoos or conditioners to help the scalp remain healthy and promote growth