The hair cycle normally consists of growing, resting and falling hairs and there is a delicate balance between these stages of hair cycle. Normally hair should re-grow but if it is not happening, you should consider seeing a dermatologist.
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The treatment typically consists of topical lotion (Minoxidil). Based on the cause of hair loss, certain specific medications can also be started. It also depends on the age of the patient and if planning for conception or not. Various issues need to be decided before initiating the treatment. The dosage and duration is decided by your dermatologist.