BALTIMORE — A new allergy risk to a common ingredient has been identified in a recent case study that has implications for vaccination. Gelatin, often found in lunchmeats, jellies, and gummy candies, is also used in vaccines, and allergy — though rare — can trigger anaphylaxis.
An allergy to egg is no longer considered a risk of flu vaccination, but investigators presenting at the American College of Allergy, Asthma & Immunology (ACAAI) 2013 Annual Scientific Meeting warned that gelatin allergy can be a problem.
It is rare, and the first case reports were published in the mid-1900s, Stephanie Albin, MD, from the Jaffe Food Allergy Institute at Mount Sinai in New York, New York, told Medscape Medical News. However, it can present significant issues because many vaccines — and foods — contain gelatin.
Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from cow, pig, and fish, she explained. Patients with gelatin allergy do not react to meat because gelatin is derived from tendons and bones rather than the flesh. And gelatin in vaccines is more likely to cause an allergic reaction because it is concentrated, purified, and processed and has direct access to the immune system through injection.
Vaccines that contain gelatin include those against influenza; measles, mumps, and rubella (MMR); varicella; yellow fever; zoster; rabies; Japanese encephalitis; and diphtheria, tetanus, and pertussis (DTaP).
The case report involved a 4-year-old boy with a presumed egg allergy who was avoiding unbaked egg upon developing a perioral rash after eating meringue icing.
"He had received the influenza vaccine in the past without any issue, but that year he developed diffuse hives, watery eyes, sneezing, and vomiting within 15 minutes of receiving the immunization," Dr. Albin reported.
A complete history of the patient's food reactions revealed that he had previously developed a watery mouth, abdominal pain, and weakness after eating gummy candies, gummy vitamins, and marshmallows. The patient was also avoiding peanuts, tree nuts, fish, and shellfish because of a family history of food allergy.
Skin-prick testing showed a 4-mm wheal and 21-mm flare with commercial egg extract, as well as a 13-mm wheal and 33-mm flare with fresh gelatin. Serum testing showed an IgE level of 4.76 kIU/L for egg white and 0.39 kIU/L for bovine gelatin. Positive IgE levels were also noted for salmon.
The patient was offered an oral food challenge to salmon with the idea that salmon-derived gelatin might be safe, but the family declined and preferred to defer any immunization with gelatin-containing vaccines, Dr. Albin said.
Gelatin-Free Alternatives
There are gelatin-free alternatives to some vaccines, including those against influenza and DTaP, but not to others, including those against zoster and MMR.
