Erythema Nodosum on the Back

Erythema nodosum is inflammation in deeper skin and commonly creates painful, warm nodules on the lower legs. Back lesions can occur, but a bump there may instead be an inflamed cyst, insect reaction, infection, pressure-related irritation or another skin condition. Location alone cannot settle the diagnosis. A clinician will consider whether the lump is deep or superficial, mobile or fixed, red or skin-coloured, and whether several similar areas are present.

Do not squeeze or puncture a back lump, especially if it is hot or increasingly painful. Reduce friction from tight clothing or backpack straps and use a cool cloth for short periods if that feels soothing. Ask someone to help photograph changes you cannot see clearly. Arrange an assessment if the lump persists, enlarges, recurs or appears with symptoms elsewhere. If the diagnosis is erythema nodosum, management may include addressing a trigger and, in selected cases, prescribed oral corticosteroid treatment.

Seek prompt medical care for a back lump with fever, rapidly spreading redness, drainage, red streaks, severe pain or feeling very unwell. Urgent assessment is also appropriate for breathing difficulty or faintness. A firm fixed lump, skin breakdown or a change that does not behave like your other nodules should not be self-treated for an extended period.

What features make this lump more or less consistent with erythema nodosum? Could friction, a cyst or infection explain it? Should I arrange follow-up if it remains?