What causes numerous small red bumps on the back?

Multiple small red bumps on the back may be caused by conditions such as folliculitis or eczema.

1. Folliculitis: The skin of the upper back contains numerous sebaceous glands and hair follicles. Moreover, the back is a region prone to sweating and oil production. Frequent熬夜 (sleep deprivation), consumption of spicy or stimulating foods, delayed bathing after exercise, or physical exhaustion can all lead to excessive sebum secretion. This excess sebum accumulates within the hair follicles and may foster bacterial growth, resulting in follicular infection—and consequently, multiple small red bumps on the back. Under a physician’s guidance, oral antibiotics—such as roxithromycin capsules or cefuroxime axetil tablets—may be prescribed for treatment.

2. Eczema: Eczema typically arises from allergic reactions triggered by various internal or external factors. For instance, some patients develop eczema after consuming spicy, stimulating, or seafood-based foods. Others may experience eczema due to contact with certain fabric materials in clothing or ingredients in cosmetics. In either case, small red bumps may appear on the back. Under medical supervision, topical treatments—such as mometasone furoate cream or hydrocortisone butyrate ointment—may be applied.