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Heeral ,I think what you have is just because of excess dry skin
and excess sun exposure ,what we call as PITYRIAISIS ALBA.Its a benign condition ,not related to any cancer.It manifests as small light colored patches on face .In your case it might be because of use of a new face wash or soap.Avoid using soap or face wash which has drying effect on face like the one which contains salicylic acid
It takes time to recover form this.What your doctor has prescribed is correct .You should just add a good moisturizer along with.Don't use desowen
or cutisoft for long (just for couple of weeks).Don't forget to use a good spf sunscreen ( i would prefer a medicated one).Also use a moisturizing soap or a face wash along with.
A skin biopsy
is a procedure where we take a small piece of skin and send it for histopathology test(its just like sending blood for investigation).I don't see a need in your case.