Most people who develop alpha-gal syndrome in the U.S. develop the condition when a Lone Star tick bites them. Bites from other types of ticks can lead to the condition in Europe, Australia and Asia.
A cancer drug that contains alpha-gal molecules also can cause alpha-gal syndrome.
Ticks that cause alpha-gal syndrome are believed to carry alpha-gal molecules from the blood of the animals they commonly bite, such as cows and sheep. When a carrier tick bites a human, the tick injects alpha-gal into the person's body.
For unknown reasons, some people have such a strong immune response to these molecules that they can no longer eat red meat without a mild to severe allergic reaction. People who are exposed to many tick bites over time may develop more-severe symptoms.
The cancer drug, cetuximab
The cancer drug cetuximab (Erbitux), which contains alpha-gal molecules, also can cause alpha-gal syndrome. Cetuximab-induced cases of this condition are most common in regions with a high population of Lone Star ticks, suggesting a possible link between Lone Star tick bites and an increased vulnerability to alpha-gal syndrome. More research is needed to understand the connection between ticks that carry alpha-gal in certain regions and cases of alpha-gal syndrome that don't seem directly linked to tick bites.
Researchers think the hallmark time-delayed reaction of alpha-gal syndrome is due to the alpha-gal molecules taking longer than other allergens to be digested and enter your circulatory system.