Miliaria, or heat rash, in darker-skinned individuals presents as small, itchy, red or flesh-colored bumps, commonly occurring in areas where sweat becomes trapped, like the back, chest, and neck. The condition is often caused by excessive sweating in hot, humid conditions, leading to blocked sweat ducts. Treatment involves keeping the skin cool and dry, using topical treatments like calamine lotion or hydrocortisone to reduce itching, and wearing loose, breathable clothing to prevent further flare-ups.