A 45-year-old man wakes with a swollen face, puffiness around the eyes and oedema of the upper lip with redness and dryness. He had no swelling, pain or dental complaints when he went to bed. Several anterior teeth have deep silicate restorations, but there is no caries, and thermal tests, percussion, palpation and periapical radiographs are all normal. His temperature is normal. The day before, he had a series of gastrointestinal radiographs with contrast medium at a local hospital. The most likely diagnosis is: