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Since you have been on medicines as well as diagnosed with T.b the immunity levels would have come down which may lead to infections of vagina as well, if this itching is associated with any white curdy discharge, it could mostly be Candidal vaginitis
Here are some tips:
1. avoid nylon undergarments, use cotton ones
2.maintain hygiene in private area, you could use LACTACYD lotion, a cleansing lotion for the vagina also prevents infections .
3. if there is curdy discharge you may use CLOTRIMAZOLE
/CANDID cream over the area before going to bed.
4. take CITREZENE tablet when you feel severe itching
5.Consult your Gynecologist for an evaluation.