Hair loss can be due to several factors and underlying causes.
Chronic hair loss is commonly due to hormonal and nutritional factors or a slow chronic toxicity.It is vital and suggested that the systemic factors are ruled out like thyroid disorder
,stress disorder,hormonal imbalance, metallic toxicity(lead,cadmium,mercury,selenium etc,)chemical toxicity(pesticides,radiation,chemotherapy
etc.).Few blood test
is to be done to rule out the systemic disorders ( especially TSH,T3/T4 etc.)and if all the tests are normal and none of the factors are contributing to your hair loss then you can follow the advice given by your dermatologist