Hard red bump on the arm

A single tender bump centered on a hair can fit folliculitis, particularly after friction, sweating, or hair removal. Many small rough bumps on the outer upper arms are typical of keratosis pilaris and may feel like fine sandpaper. A sudden itchy bump after outdoor exposure can have a different trigger. Warmth, pus, spreading redness, increasing pain, or a cluster of lesions suggests more active inflammation and warrants closer attention. Color, texture, duration, and whether the bump changes are useful details.

Wash gently, avoid scrubbing or picking, and reduce friction from tight sleeves or equipment. Do not puncture a firm bump. For rough recurring bumps, regular moisturizing may soften the surface; introduce any exfoliating product cautiously because irritated skin can become more inflamed. Photograph a changing lesion and arrange a skin assessment if it persists, grows, bleeds, crusts, or keeps returning. The right treatment depends on whether the cause is follicular inflammation, keratosis pilaris, or another diagnosis.

Seek prompt medical advice when redness expands, the area becomes hot or very painful, pus develops, or fever appears. Get urgent care for rapidly worsening swelling, red streaks, or feeling faint or seriously unwell. A bump that changes in shape, color, or surface should be examined even if it is not painful.

Ask whether the bump is folliculitis, keratosis pilaris, or another lesion, and which moisturizer or medicine is appropriate. Ask how long to monitor it and which changes should lead to earlier review.