People who had been eating steaks, barbecues and hamburgers their entire life without any problem, have suddenly developed an allergy to red meat all thanks to having been bitten by ticks.
Margaret Ann Horn, who was bitten by a lone star tick (Amblyomma americanum) commonly found in wooded areas, was diagnosed with alpha-gal allergy after she was rushed to the emergency room for severe swelling and rashes. Alpha-gal is a type of sugar found in red meat.
While Horn's case may seem bizarre, she isn't the only one who developed an allergy to red meat because of tick bites as there have been a number of other cases in Tennessee, North Carolina and Virginia. The Vanderbilt Asthma, Sinus and Allergy Program (A.S.A.P.) clinic in Nashville, Tennessee actually diagnoses one or more similar cases every week.
"It is not completely understood exactly how the allergy starts," said Robert Valet, an allergist at Vanderbilt A.S.A.P. "The thought is that the tick has the alpha-gal sugar in its gut and introduces it as part of the allergic bite and that causes the production of the allergy antibody that then cross-reacts to the meat."
Doctors have just learned that tick bites could cause food allergy after Thomas Platts-Mills, the director of the University of Virginia School of Medicine's allergy division, and his colleagues conducted an investigation and found that tick bites can cause red meat allergy.
"The results presented here provide evidence that tick bites are a cause, possibly the only cause, of IgE specific for alpha-gal in this area of the United States. Both the number of subjects becoming sensitized and the titer of IgE antibodies to alpha-gal are striking. Here we report the first example of a response to an ectoparasite giving rise to an important form of food allergy," Platts-Mills and colleagues wrote.
Allergic reactions to red meat trigger hives, swelling, vomiting, diarrhea, breathing difficulty and drops in blood pressures. The severity of the allergy also differs among patients with some having to avoid milk and foods that were cooked on the same grills used for red meat.
"I think it is something that certainly belongs among the most important food allergies, particularly in the Southeast," Valet said. "Certainly these patients can present with every bit as severe of an allergy as someone who is allergic to peanuts."
Valet said he uses blood test to confirm an alpha-gal allergy but noted that there is no good way for desensitizing people once they develop allergic reaction so they have to avoid red meat and sometimes even milk. Patients with alpha-gal allergy can safely eat poultry though including chicken or turkey but not beef, pork and venison as they can cause allergic reactions.
"It certainly is a big disruption for a lot of people's lives. Things like your classic barbecue really becomes off limits," Valet said adding that patients with alpha-gal allergy should always carry with them EpiPen, a medical device for delivering epinephrine, which is used to treat severe allergic reactions in emergency situations.
"We know that getting repeated tick bites causes the level of allergy antibody to rise and so we do recommend people with this allergy do good tick avoidance and carry an EpiPen if they do have an exposure to red meat and need to rescue themselves," Valet advised.
