A 50-year-old woman was referred after the discovery of adenoid cystic carcinoma in an excised left submandibular gland. Treatment involved clearance of the left submandibular fossa, and bilateral levels II and III selective neck dissections. A left-sided submandibular haematoma developed during the immediate postoperative period. After removal of the clot, there was a persistent, low volume capillary ooze from the left submandibular fossa and a calcium alginate fibre pack (Kaltostat) was left in place to control the bleeding. After an extended period of time the pack excited a foreign body reaction which, on a computed tomogram, mimicked a recurrence of the tumour. We review the role of Kaltostat in this setting and its potential for foreign body reaction, which may mimic serious disease.