Monday, September 10, 2012

Tick bites: A common cause of IgE antibodies to alpha-gal

By Carol Smith, MD
Birmingham Allergy & Asthma Specialists, PC

Two novel forms of anaphylaxis have been defined recently: 1) acute reactions during the first infusion of cetuximab and 2) delayed anaphylaxis to red meat.  In each case, these reactions were shown to be occurring in patients who had IgE antibodies to the oligosaccharide galactose alpha-1,3-galactose, which is a mammalian blood group substance.

In a study published in the April 2011 issue of The Journal of Allergy and Clinical Immunology (JACI), Commins et al have now reported evidence that tick bites predominantly from the Lone Star Tick cause these IgE antibodies. The evidence includes prospective data on three subjects, a strong association with a history of tick bites, a good correlation (r=0.67, p<0.001) between IgE antibodies to tick extract and IgE antibodies to alpha-gal, and finally extensive epidemiological evidence that these IgE antibodies are only found in areas where tick bites are common. These IgE antibodies are common (i.e., 15-20% of adults) in an area that includes TN, NC, AR, MO and VA.

These results are important clinically because the cases of anaphylaxis starting 3-6 hours after eating beef, lamb or pork can be very confusing. The history usually includes prolonged pruritic reaction to ticks. The diagnosis becomes probable with positive skin tests to mammalian extracts and can be confirmed by blood test for IgE to alpha-gal.

This comes from the website of the American Academy of Allergy, Asthma and Immunology. These novel forms of delayed pruritus, urticarial and/or anaphylaxis have been elucidated, primarily through research done in the Allergy Department of the University of NC, Chapel Hill. We have diagnosed several cases here at the Birmingham Allergy & Asthma Clinic, but many more cases likely go undiagnosed. Please let us know if you have any patients with delayed or unexplained anaphylaxis, or questions about this very interesting phenomenon.

Birmingham Allergy & Asthma Specialists, PC

1 comment:

  1. My husband died last year because of having tick bites and being given Erbitux. We live in GA. Patients need to be told about this allergy. Erbitux should not be used in the southeast - it is too dangerous and what is even worse. The drug maker knows about this and have known since 2008 when Dr Platts-Mills discovered the allergy and TOLD them.