Pimples on the back are usually a form of body acne caused by sweat, oil, and clogged pores. You can help reduce them by keeping the area clean, bathing after sweating, wearing loose cotton clothes, and avoiding oily or tight clothing. Using a medicated body wash or cream containing ingredients like benzoyl peroxide or salicylic acid can be helpful. Avoid picking or squeezing the pimples, as this can worsen them.