Whenever i get warm my back itches like crazy. it feels like pins sticking in. how can i treat this.

Check it out: Metabolic or allergic issues may be in play. See your doc.

Common: This sounds like something called prickly heat, a common problem involving your sweat glands, or even dry skin. How often you shower/bathe, what soap you use, lotions you can try, and clothing you wear can all contribute. Minimize daily bathing, use mild soap, try a good moisturizing lotion after bathing and consider cotton or microfiber shirts.

Dry skin?: You may have dry skin. Try avoiding scented or antibacterial soap and applying a moisturizer over your back if not the entire body immediately after bathing and see this helps (may take a few days). See dermatologist if problem persists.