Nancy, a 45 –year-old park ranger, developed generalized hives, dizziness and difficulty breathing 4 hours after she ate a beef steak. She recalled being bitten by ticks frequently since she works at the national park.
While 90% of food allergy is from peanut, tree nut, fish, shellfish, wheat, soy, milk and egg, meat allergy is extremely rare. Food allergy occurs in some people with a genetic predisposition to developing antibodies (IgE) to specific proteins (allergens) in the food. In general, food allergy symptoms occur from within minutes to several hours after eating an offending food. The onset of severe anaphylactic reaction is always immediate.
Since 2008, over 1500 cases of meat allergy linked to tick bite have been reported. The link between meat allergy and tick bite is both unexpected and fascinating. Tick-triggered meat allergy may have gone unnoticed for years due to its unusual presentation of a delayed reaction. Tick-triggered meat allergy is a food allergy, not a disease like Lyme disease or Rocky Mountain Spotted Fever.
Meat allergy occurs in some people with a genetic predisposition to developing anti-alpha-gal antibodies after a tick bite, especially that of the Lone Star tick. Four to six hours after consuming the meat, the anti-alpha-gal IgE antibodies in the victim’s blood react to alpha-gal in the meat (beef, lamb, pork), then trigger chemical mediators to release which causes the unusual delayed allergic reaction. This delayed reaction occurs because alpha-gal is most concentrated in animal fat, which takes several hours to digest. Alpha-gal’s reactions vary from case to- case, with some patients experiencing a severe reaction while others none at all.
In a majority of cases, tick bites have become a concern for meat-loving hikers, farmers and nearly anyone who spends regular time outdoors in the Southeastern states like Virginia, Kentucky and Tennessee where the Lone Star tick is commonly found.
The distribution, range and abundance of the Lone Star tick has increased steadily in the past 20-30 years, probably due to concurrent rising of the population of its natural host, white-tailed deer and wild turkey. Moreover, there are new cases recently found outside of the Lone Star tick area. Therefore, Lone Stars may not be the only tick carrier. Another type of tick, ixodes holocyclus, has been reported in other countries, such as Australia, Spain, France and Sweden.
Currently, there are only a few laboratories capable of measuring anti-alpha-gal IgE. In the meantime, people with a history of meat allergy and tick bite should avoid eating meat. Patients with history of tick-triggered meat allergy should keep an Epi-pen available. The good news is that the allergic reaction seems to fade after a few years in some sufferers, providing they avoid additional tick bites.