What should you know about a small painful lump under the skin?

A small painful lump under the skin may come from inflammation, an infected follicle, a boil, or another skin condition, so its location and changes over time matter. The surface may look normal at first, or it may become red, warm, swollen, or tender. A clinician may need to examine the lump to distinguish a blocked follicle, collection of pus, inflamed cyst, or a rash-related problem. Do not squeeze, pierce, or cut it at home, because this can irritate the tissue and spread infection.

A boil is a tender, inflamed lump that can develop around a hair follicle and may later form a central area of pus. Repeated painful lumps in the armpits, groin, under the breasts, or between the buttocks can occur with hidradenitis suppurativa. Diffuse redness, warmth, swelling, and pain around the lump may point to cellulitis, while burning or pain followed by a one-sided blistering rash can occur with shingles. These patterns are clues, not a diagnosis: the same symptom can have different causes depending on the body area, duration, skin changes, and your general health.

Keep the area clean and avoid friction from tight clothing, shaving, or repeated touching. A warm, clean compress may make a superficial tender lump more comfortable; stop if the skin becomes more irritated. If it opens, let it drain naturally, cover it with a clean dressing, wash your hands after contact, and avoid sharing towels. Note when it appeared, whether it is enlarging, and whether redness is spreading. Arrange a dermatology or primary-care assessment if it does not settle, keeps returning, or makes movement uncomfortable. Treatment depends on the cause and can include prescribed medicine or a clinician-performed procedure such as abscess drainage.

Seek prompt medical care if the lump is rapidly enlarging, the surrounding redness is spreading, or the area is markedly hot, swollen, or painful. Fever, chills, feeling faint, red streaks, pus with worsening pain, or a lump near the eye or nose also warrants urgent assessment. Seek emergency help for confusion, severe weakness, breathing difficulty, or swelling of the face or throat. People with diabetes, reduced immunity, or medicines that suppress immunity should contact a clinician early when a painful lump appears.

You can ask: What features make this more consistent with a boil, cyst, cellulitis, shingles, or another cause? Does it need a swab, imaging, prescription treatment, or drainage? What changes should make me return sooner? If similar lumps recur, could the pattern suggest hidradenitis suppurativa or an irritated hair follicle? Bring a list of medicines, relevant health conditions, and photos showing how the area changed.