Meat Allergy


Serum Albumin Allergy (Mammals and Poultry)

  • Serum albumins are heat labile
  • This type of food allergy is usually due to cross-reactivity
    • Sequence homology between bovine serum albumin (BSA) and pig, sheep, and chicken serum albumins were 80, 92, and 44% supporting observation that patients allergic to beef may react to mutton or pork, but rarely to poultry (goose, duck, turkey, and chicken meat) or fish, and other patients may react to poultry, but not to mammalian meats

  • Examples
    • Cow's meat and cow's milk
      • Almost all children allergic to beef are allergic to milk; 10-20% of children allergic to milk are allergic to beef
      • Industrial treatment (freeze-dried, homogenized) more than cooking beef well may modify the allergic reactivity of this meat in beef-allergic children. Cooked processed beef may be safer alternative to raw meat cooked at home.
      • Total avoidance of beef by all cow’s milk-allergic children is not justified. In this setting "an allergist’s evaluation of cross-sensitization makes sense during the diagnostic work-up of milk allergy."
    • Pork - cat syndrome
      • Food allergy (from oral itching to anaphylaxis) to pork due to cross-reactivity between pork serum albumin and cat serum albumin (Fel d 2)
      • In most cases, these patients have cat exposure (often ownership), positive SPT to cat dander or pork, and inconsistent (due to effect of cooking?) immediate (not delayed) reactions after eating pork, but tolerate beef
      • Platts-Mills: in these cases, sIgE to pork, beef, cat serum albumin, and alpha-gal is recommended



Galactose-a-1,3-galactose (alpha-gal) Red Meat Allergy (Mammals)



BackgroundLone Star Tick Geography.png

  • Alpha-gal is an allergenic oligosaccharide (cross-reactive carbohydrate determinant) present on cells of all non-primate mammalian species (e.g. beef, pork, lamb) and on the Fab fragment of the monoclonal antibody cetuximab (Erbitux, used for colorectal and head and neck cancer)
  • The alpha-gal epitope is a major blood group substance of nonprimate mammals and structurally related to human blood group B
  • Bites from certain species of ticks can induce both IgE to tick proteins and to alpha-gal, and can induce new onset allergy to mammalian foods containing alpha-gal and to cetuximab
    • Reported in states where the lone star tick (Amblyomma americanum) is found, and there are case series from Northwestern Spain, France, Sweden (where the Ixodes ricinus tick is found) and Australia (where the Ixodes holocyclusis found)
      • Note that the lone star tick is the primary vector for Ehrlichiosis
      • Bites from the lone star tick are often severely pruritic and may persist for weeks (vs bites from deer ticks (Lyme disease vector) which are not pruritic and do not induce IgE to alpha-gal)


Clinical Features

  • Clinical features of alpha-gal food allergy include delayed onset generalized urticaria or anaphylaxis starting 3-6 hours after eating beef, pork, or lamb. Some also have reactions to milk, which contains alpha-gal.
    • Children are more likely to have urticaria than anaphylaxis
    • In cases of new onset cow's milk allergy >5 years old, alpha-gal should be considered as an alternative diagnosis to protein-based milk allergy
  • Most are sensitized to mammal-derived gelatin (which contains alpha-gal), and a subset will be clinically allergic to both red meat and gelatin
  • In one study, almost all affected patients have B negative blood type (e.g. A or O); the alpha-gal epitope is a major blood group substance of nonprimate mammals and structurally related to human blood group B
  • Most are sensitized to cat (via SPT/sIgE) due to alpha-gal found on cat IgA (Fel d 5w); note that the current ImmunoCAP for cat primarily detects sensitization to Fel d 1
  • Some patients have noted significant local irritation/urticaria that can occur after handling meat, particularly if they have open sores, cuts, or cracks in the skin of their hands


Testing

  • SPT to meat usually small (2-5 mm) or negative, ID to meat may be positive, prick-by-prick testing with fresh meat and cetuximab may be considered
  • sIgE (ImmunoCAP) testing may be more sensitive at detecting sensitization to meat-derived allergen than skin testing
  • Consider obtaining blood type
  • Specific IgE test for alpha-gal is available commercially (Viracor IBT, Thermo Scientific) and at University of Virginia (Tel 434-924-2291)
  • Oral food challenge with appropriate duration of observation
    • Small amounts of meat (1 strip of bacon) is frequently tolerated but 2 pork sausage patties (~86 g) reliably induces symptoms; larger amounts (e.g. plate of barbeque) associated with increased severity of reactions
    • Fattier cuts of beef (ribs) more likely to elicit reaction than lean (deli ham or tenderloin)
    • Positive food challenge more likely with recent tick bite booster (within 1-4 weeks), as the alpha-gal sIgE level seems to decrease with time if there are no additional bites
    • Because of the delayed symptom onset, incremental dosing is not possible (the entire dose must be given at the start of the challenge)
    • Itching is often the first symptom that appears


Management

  • Routine management of food allergy (avoidance of all mammalian meat/organs, Epipen, etc.)
  • Check alpha-gal sIgE every 8-12 months, as some patients (adult and pediatric) can tolerate mammalian meat again after avoiding additional tick bites for 1 to 2 years
  • Reaction seems to be related to quantity of meat ingested, therefore may consider complete elimination of meat or allowing continued ingestion of quantities of meat that have been previously tolerated 2-3 times a week


Note
  • Tissue-specific allergy to pork gut and kidney with tolerance of pork meat has been described
  • Allergy to poultry meat has been reported in adults who tolerate poultry eggs, feathers, and dander
  • Comparison of allergens/syndromes involved in cat inhalant allergy, pork-cat syndrome, and alpha-gal allergy:
    cat-tick alphagal chart.png

Differential Diagnosis

  • Allergic reactions to antibiotics in meat
  • Adverse reactions to naturally occurring chemicals or preservatives in meat



References