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preet ,if you have hair loss due to allergy then it won't cause thinning of hair ,instead there would be loss of hair in groups from the roots.Along with this you would also have itching on scalp. I am sure you don't have this or any kind of allergy.In fact you should get your thyroid
check up done with serum iron
level & hemoglobin
also tested.These are more important reasons for thinning of hair and hair loss.It can also be genetic or hormonal
if you have M shaped hair loss.
Shaving off your hair is not an answer at all.You are not going to gain anything out of it.Its a myth that one gets thicker hair after shaving off.
You should meet a dermatologist
and take his opinion on this.