Acne on the back and arms (often called body acne) is usually caused by clogged pores from sweat, oil, friction from tight clothing, or sometimes dandruff and hormonal factors, even if your face is clear. Treatment includes keeping the skin clean by bathing soon after sweating, wearing loose cotton clothes, and using a body wash containing salicylic acid or benzoyl peroxide to help unclog pores and reduce bacteria. Avoid picking or scrubbing harshly, as this can worsen the condition and cause marks. If the acne is persistent or severe, a dermatologist may prescribe stronger treatments such as topical retinoids or oral medicines. Consistency with these measures usually leads to good improvement over time.