Tick bite turns red meat into nasty allergy

Washington - Waking up at midnight with breathing difficulties and in a state of shock could be due to a severe allergic reaction (delayed anaphylaxis) to red meat, warn researchers.

Delayed anaphylaxis, triggered by a tick bite, is a new syndrome identified initially in the southeastern US. Patients may wake up with hives (urticaria or red rashes that spring up all over the skin) or anaphylaxis usually three to six hours after having eaten red meat for dinner. Until recently, the link between red meat and anaphylaxis had remained elusive.

Significantly, anaphylaxis is the also the first food-induced severe allergic reaction due to a carbohydrate rather than a protein. It is also the first time anaphylaxis has been noted to be delayed rather than occurring immediately after exposure, the Journal of General Internal Medicine reported.

Susan Wolve and Diane Sun, from Virginia Commonwealth University, US, and colleagues identified the allergic reaction as being caused by antibodies to a carbohydrate (alpha-gal), produced in a patient's blood in response to a tick bite, specifically the Lone Star tick.

This carbohydrate substance is also present in meat. When an individual who has been bitten by a tick eats the meat, his or her immune system activates the release of histamine in response to the presence of alpha-gal, which can cause hives and anaphylaxis, according to a university statement.

Histamine is a compound in mammalian tissues that causes dilatation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion, that is released during allergic reactions.

The authors concluded: "Where ticks are endemic, clinicians should be aware of this new syndrome when presented with a case of anaphylaxis. Current guidance is to counsel patients to avoid all mammalian meat - beef, pork, lamb and venison."

Respiratory symptoms occur in about 70 percent of reactions, and are especially common in people who also have asthma or another chronic respiratory disease. Extremely low blood pressure, causing light headedness, dizziness, blurred vision, or loss of consciousness (passing out) occurs in about 30 percent of reactions.