What causes cysts beneath the skin on the lower back?

Cysts : There are times when an injury or inflammmed hair follicle will develop a cyst . Other times it is random. See a dermatolgist if the cysts are enlarging or becoming red or sore.

Blocked pore: Epidermoid cysts are started with a blocked pore that can't exude skin cells normally onto the skin. Factors that encourage blocked pores which might lead to forming a cyst are tight clothing, waistbands, & straps which is why cysts are often found on the back. They are not usually problematic unless they rupture and become inflamed.