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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Start on biotin supplements and food rich in iron content. Use a milder shampoo and consider frequent shampooing and conditioning.
You can consult me on Practo Direct for personal recommendations as on public platforms, I cannot generate a prescription.