Risk factors

Doctors don't yet know why some people develop alpha-gal syndrome after exposure and others don't. The condition mostly occurs in the southeastern United States and parts of New York, New Jersey and New England. You're at increased risk if you live or spend time in these regions and:

• Spend a lot of time outdoors
• Have received multiple Lone Star tick bites
• Have a mast cell abnormality such as indolent systemic mastocytosis

In the past 20 to 30 years, the Lone Star tick has been found in large numbers as far north as Maine and as far west as central Texas and Oklahoma in the United States.

Alpha-gal syndrome can also occur in other parts of the world such as Europe, Australia and parts of Asia, where bites from certain types of ticks also appear to increase your risk of the condition.