Gelatin Allergy

Gelatin allergy is an IgE-mediated reaction to gelatin, a protein made from bovine or porcine collagen, found in foods, vaccines, capsules and plasma expanders. It is uncommon but can cause anaphylaxis.

Pathophysiology. Sensitisation occurs through vaccines containing gelatin stabiliser, through foods, or through galactose-alpha-1,3-galactose after tick bites (alpha gal syndrome). Cross-reactivity exists between bovine and porcine gelatin, and gelatin in some cases carries alpha gal.

Hydrolysed gelatin is less allergenic, and gelatin containing live vaccines (older measles-mumps-rubella and varicella formulations in some regions) were the main cause of vaccine reactions.

Reactions may occur with a delay of several hours if alpha gal is the target.

• Urticaria, angio oedema, flushing within minutes of exposure
• Vomiting, abdominal pain, diarrhoea
• Wheeze and throat tightness
• Anaphylaxis after gelatin colloid infusion, gelatin containing vaccine or capsule
• Reactions to marshmallow, gummy sweets, jelly, aspic, and gelatin containing capsules or suppositories
• Delayed reactions to mammalian meat if alpha gal syndrome is the underlying cause

• History: exposure to gelatin foods, vaccines, medicines and colloids, and tick bites.
• Skin prick test and specific IgE to gelatin (bovine and porcine): positive results support sensitisation.
• Specific IgE to alpha gal to exclude alpha gal syndrome.
• Intradermal testing with the gelatin containing product when the culprit is unclear.
• Tryptase during a reaction.
• Supervised oral challenge is rarely needed, and carries a risk of severe reaction.

Differential diagnosis.

• Alpha gal syndrome
• Cow's milk and egg allergy (other vaccine excipient reactions)
• Allergy to other vaccine components (egg, yeast, latex, neomycin)
• Mast cell disorders
• Idiopathic anaphylaxis
• Reactions to other plasma expanders

• Avoid gelatin in food, capsules, suppositories and gelatin colloid plasma expanders (use crystalloid or other colloids).
• Vaccines: use gelatin free preparations when available. When a gelatin containing vaccine is the only option, vaccinate under specialist supervision, with testing and observation.
• Medicines: use tablets or vegetarian capsules in place of gelatin capsules.
• Mild reactions: cetirizine 10 mg orally once daily in adults (children 1 to 5 years 2.5 mg twice daily; 6 to 11 years 5 mg twice daily).
• Anaphylaxis: adrenaline 0.5 mg intramuscularly (children 0.01 mg/kg, maximum 0.5 mg) into the anterolateral thigh, repeated after 5 minutes if no improvement, plus oxygen and intravenous fluids, and observation for at least 6 hours.
• Adrenaline auto injector for systemic reactions: 150 microgram for 7.5 to 25 kg, 300 microgram for 25 to 50 kg, 500 microgram for over 50 kg, with a written action plan and training.
• Alpha gal syndrome: if present, avoid mammalian meat and tick bites.
• Medical alert: record gelatin allergy and inform anaesthetists before surgery.

Special groups.

• Children needing live vaccines: check the gelatin content of the specific product and seek allergy advice.

Monitoring. Review every 12 months. Check auto injector dose and expiry. Repeat alpha gal specific IgE if tick exposure continues.

Referral and escalation. Refer to allergy for any suspected reaction to a vaccine, colloid or capsule. Emergency for anaphylaxis.