Blood-Filled Lump Under the Skin: What to Do

A deep red or purple lump may be a collection of blood after a knock, injection, or other injury. It might instead be an inflamed cyst, a boil containing pus and blood, or a lesion arising from skin structures or blood vessels. The colour seen through the skin does not reveal the contents with certainty.

Boils often present as increasingly tender, warm lumps that may form a pus-filled centre. Basal cell carcinoma more often presents as a slowly changing skin lesion that may look pearly, ulcerate, crust, or bleed; it is not diagnosed simply because a lump looks blood-filled. Examination preserves the correct direction between a condition and its possible presentation.

Avoid pressing, massaging, cutting, or draining the lump. Protect it from repeated impact and make a note of any recent injury or procedure. Record whether it feels soft, firm, fixed, or mobile and whether the overlying skin changes, but do not repeatedly manipulate it to test these features.

A clinician may inspect and feel the area, then decide whether observation, imaging, treatment for inflammation, or sampling is warranted. An intralesional steroid injection is useful only for selected inflammatory lesions and should not be placed into an unidentified lump or an area with suspected infection.

Seek prompt assessment when the lump enlarges quickly, becomes hot or very tender, drains pus, causes spreading redness, or is accompanied by fever. Review is also needed when there was no clear injury, the lump feels hard or fixed, it remains present, or the skin over it repeatedly crusts, ulcerates, or bleeds.

Obtain urgent care if swelling threatens breathing or swallowing, severe pain follows an injury, a limb becomes numb or pale, you feel faint, or active bleeding will not stop with firm pressure. Tell the clinician about medicines that affect clotting and any condition that weakens immune defence.

Ask which features suggest blood, infection, a cyst, or a solid growth; whether imaging would show its depth; and whether a sample is needed before treatment. Also discuss what activity is safe, how to manage discomfort, and which specific change warrants earlier follow-up.