A lump that becomes painful, red, hot or swollen may be infected. Common causes include a skin abscess, an inflamed cyst or infection around a hair follicle. Symptoms can worsen quickly as pus collects beneath the skin. Early assessment is important because antibiotics alone may not treat a well-formed abscess and a drainage procedure may be required.
Signs of an abscess or infected cyst
The area may feel tender, warm and increasingly tense. Redness can be less obvious on brown or black skin, so increasing heat, pain and swelling are important signs. The centre may soften, develop a white point or begin leaking pus. Fever, chills or feeling generally unwell can suggest that the infection is spreading.
What causes the swelling?
Bacteria can enter through a small break in the skin or blocked follicle and form a collection of pus. A pre-existing epidermoid or pilar cyst may become inflamed or infected. Recurrent abscesses can be associated with diabetes, smoking, immune suppression or conditions such as hidradenitis suppurativa. A pilonidal abscess specifically develops in the cleft between the buttocks.
How is it assessed?
Diagnosis is often made through examination. Your clinician will assess the size, depth and location of the collection and whether cellulitis is present. Ultrasound may help when the swelling is deep or it is unclear whether pus has collected. A sample may be sent for testing in recurrent, severe or unusual infections.
Treatment
A small early infection may sometimes respond to local care or antibiotics, but a mature abscess often needs incision and drainage. A small opening is made so pus can escape, usually under local anaesthetic. The wound may be left open and require dressings. If an infected cyst remains after inflammation settles, later complete excision may help prevent recurrence.
When should I seek urgent help?
Seek urgent medical attention for rapidly spreading redness, severe pain, fever, confusion, fast breathing, facial swelling or infection near the eye. People with diabetes, immune suppression or pregnancy should seek advice promptly. Do not squeeze or puncture the lump at home.
Frequently asked questions
Will antibiotics cure an abscess? Antibiotics may be needed, but a collection of pus often requires drainage.
Can an abscess come back? Yes, especially if an underlying cyst, sinus or risk factor remains.
Can I drain it myself? No. Squeezing can spread infection and delay appropriate treatment.