When I hear people complaining about allergies and wine, usually they're blaming sulfites (and often wrongly). Or sometimes it's the histamines that cause problems - this often happens to me. But usually, wasp venom is the last thing that comes to mind. According to a group of Spanish doctors, however, it seems that it is indeed the root of allergic reactions some people are experiencing. It's likely that wasps accidentally were crushed with the grapes (they were probably attracted to the over-ripe fruit).

From New Scientist:

Alicia Armentia of the Rio Hortega Hospital in Valladolid, Spain, and her colleagues treated five people who had developed severe allergic reactions after drinking either wine or grape juice. Three of the patients had facial flushing and swollen lips, while another experienced asthma-like symptoms. The fifth patient developed anaphylaxis, a whole-body allergic reaction that can cause death as a result of constricted airways.

Armentia and her colleagues successfully treated all of these patients, but they remained baffled over the cause of the allergic responses. A battery of tests on the patients ruled out the most likely suspects, such as egg white, which is sometimes added to wine to clarify it and reduce harshness, and grape extract.

More elaborate analysis of the patients' blood revealed antibodies suggesting a recent bee or wasp sting. However, none of the patients reported being stung. So the doctors looked for allergic responses to red and white grape juice, along with a newly pressed wine and three aged wines, all from different vineyards.

Both types of juice and the freshly made wine all triggered reactions in blood samples taken from the patients. Further chemical tests provided strong evidence that this was due to trace amounts of venom from yellow-jacket wasps - not from bees - in the beverages.