What is red meat allergy
Patients often self-diagnose alpha-gal allergy by using online sources of information, oral food challenges, and logical reasoning .
The most precise method of diagnosing tick bite induced allergy is by testing for IgE titres against the alpha-gal molecule. However, the high cost and lack of availability of this test limit its use .
IgE-associated food allergies are generally tested for by prick testing. The protocol and accuracy of the prick test for alpha-gal allergy are debated, as delayed reactions and false-negative results are reported .
What are the complications of tick bite induced red meat allergy?
The main complication of tick bite induced red meat allergy is anaphylaxis, which can be life-threatening.
Anaphylaxis signs and symptoms include airway constriction, swelling of the throat, a severe drop in blood pressure, a high pulse rate, and dizziness.
What causes tick bite induced red meat allergy?
The details of how a tick bite leads to allergic reactions to red meat and other substances are not completely understood.
The species of ticks that cause alpha-gal allergy include:
- The castor bean tick (Ixodes ricinus) found in Europe
- The species Ixodes australiensis,found in Australia
- The lone star tick (Amblyomma americanum)found in theUnited States
- The paralysis tick (Ixodes holocyclus) found in Australia
- An unknown species found in South Africa and other regions .
The tick injects saliva containing alpha-gal into the skin of its victim.
Sensitisation to alpha-gal is associated with the development of specific IgE antibodies to the carbohydrate.
The component of alpha-gal that causes sensitisation is not known .
The symptoms of the subsequent reaction to red meat are typical of most food allergies, except the reaction is delayed by several hours and the antigen is a carbohydrate in the meat rather than a protein. More severe reactions can happen in people exposed to multiple tick bites.
Red meat is defined as every meats obtained from mammals and includes beef, pork, and lamb. The meat is red because of the high concentrations of myoglobin.
Meat obtained from birds such as chicken or turkey is white meat and does not generate an allergic response due to lack of alpha-gal.
Other substances can cause the same allergic response.
- Anticoagulants and bioprosthetic heart valves made from porcine intestines contain alpha-gal.
- Intravenous fluid replacements that contain gelatine may cause reactions in individuals sensitised to alpha-gal .
- Cetuximab (an anti-cancer drug) is a chimaeric mouse and human monoclonalantibody and contains alpha-gal.
- Alpha-gal in gelatin, milk, whipped cream, and cheese could also elicit an allergic response .
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 every mammals except humans and Ancient 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 hard. 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
- Bircher AJ, Hofmeier KS, Link S, Heijnen I.
Food allergy to the carbohydrate galactose-alpha-1,3-galactose (alpha-gal): four case reports and a review.
Eur J Dermatol 2017; 27: 3-9.
- Fischer J, Yazdi AS, Biedermann T. Clinical spectrum of alpha-Gal syndrome: from immediate-type to delayed immediate-type reactions to mammalian innards and meat. Allergo J Int 2016; 25: 55–62.
- Commins SP, Platts-Mills TAE. Delayed Anaphylaxis to Red Meat in Patients with IgE Specific for Galactose alpha-1,3-Galactose (alpha-gal). Curr Allergy Asthma Rep 2013; 13: 72-77.
- Steinke JW, Platts-Mills TAE, Commins SP.
The alpha gal story: Lessons learned from connecting the dots. J Allergy Clin Immunol 2015; 135: 589-597.
Small Intestine: Introduction and Index
Small Intestine: Introduction and Index
Updated May 2019. Send comments to [email protected]
What is tick bite induced red meat allergy?
Tick bite induced red meat allergy is an allergy to the carbohydrate galactose-alpha-1,3-galactose (also known as alpha-gal), which is present in both tick bite saliva and red meat .
Tick bite induced red meat allergy is also called alpha-gal allergy.
Sensitisation to alpha-gal follows a bite from certain species of tick. Subsequently, eating red meat may result in itching, urticaria, angioedema, gastrointestinal upset, and rarely, anaphylaxis .
Who gets tick bite induced red meat allergy?
The incidence of tick bite induced red meat allergy is unknown .
It is associated with a history of tick bites, atopy, and cat ownership . Multiple tick bites increase the risk.
The allergy arises in people exposed to the ticks due to geographic location or occupation. For example, forest service employees and hunters in certain countries are at higher risk of carrying alpha-gal‐specific IgE and developing red meat allergy compared to a resident population in the same region .
Systemicmastocytosis can increase the risk of acquiring tick bite induced red meat allergy .
What are the clinical features of tick bite induced red meat allergy?
The delayed allergic reaction which follows is typical of food allergy, except that symptoms start 3–8 hours after ingestion of red meat, whereas other food allergies happen within minutes of exposure to the allergen .
On rare occasions,anaphylaxis can occur.