If your skin on back is dry and pigmented:

Smooth back: Mix besan (gram flour), curd and lemon juice.
Apply it on your back daily. After 20 minutes, scrub the paste off with a long-handled loofah, and rinse.
Blemish-free back: Mix equal quantities of lemon juice and cucumber juice.
Apply it on the dark patches every day. Rinse after 20 minutes.

– Shahnaz Husain