Gelatin is an animal derived proteinaceous substance found in food, cosmetics and medical supplies. It is derived from collagen that is partially hydrolyzed from either pig or cattle. This leads to a gel forming property that gives texture to foods such as marshmallow and jelly. It is also used to make pill capsules, agents that stop bleeding and vaccines. Gelatin allergy can be problematic as it is sometimes hidden in medical supplies.
Gelatin can be used in pharmaceutical products as:
- Binder-imparts cohesive qualities to the powdered material
- Gelling agent-capsule shell material
- Gelling hydrocolloid-substances that cross-link and increase viscosity
Gelatin allergic reactions have been well documented in the past. Reported triggers have included vaccines (MMR, Zoster, Varicella), hemostatic agents (Gelfoam, Floseal, Surgifoam), IV colloids, medicine capsules (Advil Liqui-gels) and other surgical tools. Anaphylaxis was the most common outcome, with fatalities reported. Many described patients in the literature experienced their first reaction to gelatin in the operating room. Some patients had previously tolerated gelatin in the form of Jell-O, certain yogurts, pork and other meats, as well as vaccines.
MMR vaccine reactions were thought to be from egg allergy in the past. But later it was revealed that it was actually gelatin. Gelatin is added to vaccines because it allows for greater heat stability, permitting vaccine distribution in developing countries. Its been used in Flumist, MMR, rabies vaccines, varicella, yellow fever, zoster (Zostavax) and oral typhoid. It is important to review vaccine-prescribing information because some forms contain gelatin and others do not. In addition, vaccine ingredients may change year to year.
Gelatin is frequently added to medicine formulations as a binding, gelling or encapsulating agent. This poses a significant risk for patients with severe gelatin allergy. Inciting agents have included cold medications, vaginal antimicrobial capsules and anesthetic suppositories. Package inserts are reliable sources of information that specify gelatin content.
Patients allergic to bovine (cattle) gelatin show high cross reactivity to porcine (pig) gelatin and vice versa. Gelatin is used to process many foods (marshmallows, food thickeners, dips, glazes, icings, yogurts, mayonnaise, ice cream, sausage coatings, salami, tinned ham, pate, meat stock, fruit juices and wines). An increasing number of cases of clinical gelatin allergy occurring together with red meat allergy are being described. Results of gelatin and alpha gal IgE testing were significant associated.
Although most gelatin is sourced from cows and pigs, fish gelatin is of increasing interest in religious communities who don’t eat pig. Fish gelatin is a food additive that can be derived from fish skin. Although typical doses of fish gelatin are tolerated by most fish allergic individuals, anaphylaxis from fish gelatin has been described.
Gelatin allergy is an infrequent but important allergen. Its diagnosis can be challenging, but it should be considered in unknown anaphylaxis. In 2019, gelatin remains an underappreciated ingredient found throughout the health care system, and vigilance needs to be high if a patient is found allergic to it. Allergy IgE testing by an allergist can be performed to help diagnose it.