For years we've been hearing that you can't get a flu shot if you have egg allergies. Viruses are not able to reproduce on their own; they have to infect living cells and exploit their host's molecular mechanisms for producing new proteins and DNA or RNA strands. Chicken eggs are convenient sources of living cells. The manufacturers of flu vaccines use eggs to grow the influenza virus, so the final vaccine contains traces of residual egg protein. This presents a theoretical risk of allergic reactions, including anaphylaxis, in individuals with egg allergies.
Egg allergy is one of the most common childhood food allergies. Most children develop a tolerance for eggs, but some continue to experience sensitivity into adulthood. Symptoms range from mild to life threatening, including:
1. Skin rash,
2. Hives,
3. Vomiting,
4. Inflamed nasal passages,
5. Rare cases of anaphylaxis, which is a severe systemic allergic reaction.
Mild allergic reactions may be much less of problem than a case of the flu. Therefore, medical researchers are taking a second look at whether the flu shot is safe for individuals with egg allergy.
In a Canadian study of 830 patients with confirmed egg allergy, flu shots did not cause any cases of anaphylaxis. Patients with a history of respiratory or cardiovascular reactions to eggs were vaccinated with two shots, 30 minutes apart. The first shot contained only 10 percent of the normal dose, and the second contained the remaining 90 percent. All subjects were observed for 60 minutes after vaccination, and assessed for delayed reactions 24 hours later.
Nine patients had minor allergic reactions and were treated with antihistamines. Three others were treated with salbutamol for respiratory reactions.
The Mayo Clinic web site recommends that you consult your doctor before getting the flu shot if you or your child has egg allergies. A skin test can help predict your risk of allergic reaction. If the test is positive, you may want to choose the divided dose option with at least 30 minutes of observation in a doctor's office, where you or your child can be treated for allergic reactions.
References:
1. Gagnon R et al, “Safe vaccination of patients with egg allergy with an adjuvanted pandemic H1N1 vaccine”, J Allergy Clin Immunol. 2010 Aug; 126(2): 317-23.
2. Benhamou AH et al, “State of the art and new horizons in the diagnosis and management of egg allergy”, Allergy. 2010 Mar; 65(3): 283-9.
3. More information online:
http://www.mayoclinic.com/health/egg-allergy/DS01021
http://www.mayoclinic.com/health/flu-vaccine-egg-allergy/AN02033
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.