Digestive System > Small Intestine

Allergic Reactions to Red Meat

Allergic reactions to mammalian-origin meats are rare but seem to be increasing in frequency in both adults and children. An impressive body of scientific sleuthing revealed this life-threatening problem to result from an immunoglobulin E (IgE)-mediated antibody response to the carbohydrate (oligosaccharide) galactose- α-1,3-galactose, commonly referred to as α-gal.

The α-gal molecule is a normal component on muscle and organs from all mammals except humans and Old World Monkeys. It is also absent in tissues from fish and poultry. Thus, α-gal is an immunologically foreign molecule to humans and they can become sensitized to it and suffer sometimes severe allergic reactions upon exposure. Thus, humans that become sensitized to α-gal and consume red meat that bears the α-gal molecule may suffer severe, sometimes lethal allergic and anaphylactic reactions. In contrast to most food allergies, such allergic reactions typically develop several hours after consumption of red meat, making diagnosis somewhat difficult. The most common initial reaction of individuals that develop red meat allergies is itching, sometimes associated with hives, edema and, most seriously, anaphylaxis.

How to people become sensitized to α-gal? The best-studied mechanism for sensitization is from tick bites. Although some details remain unknown, epidemiologic and prospective studies indicate that bites from several types of ticks (some species of Amblyomma and Ixodes) induce humans to develop of IgE antibodies to α-gal. Exactly how tick bites result in allergic sensitization is poorly understood, but may involve deposition of α-gal from a previous blood meal (e.g. a deer) into the patient, resulting in development of an immune response.

Sensitization by tick bite appears to account for roughly 80% of the cases of red meat allergy, but other mechanisms exist. There are also related conditions, such as the "pork-cat syndrome", where people become sensitized to cat dander or other substances and suffer from allergy to pork, but interestingly, not to beef.

References and Reviews

Small Intestine: Introduction and Index

Updated May 2019. Send comments to Richard.Bowen@colostate.edu