While seldom mentioned, it is possible to have an allergic reaction to the flu vaccine. The influenza immunization contains “foreign” proteins, which can provoke an allergic reaction. While the vaccine is well-tolerated by the majority of people, as long as any immunization contains proteins from other animals or substances as well as chemical components, it will be possible to have a dangerous complication due to allergies.

The US Centers for Disease Control and Prevention say that there are certain people who should not get an influenza shot without consulting with their family physician (or allergist) first:

1. Anyone with an egg allergy could have an allergic reaction to the flu vaccine. The flu vaccine is made by growing the selected virus strains in hen’s eggs. The vaccine is then purified and all live virus killed with a chemical such as formaldehyde. All the components used to develop the vaccine will remain in the final product to some degree. As a result, if you have a severe egg allergy, you can have a reaction to the small quantity of egg proteins that remain in the vaccine. If you have severe chemical sensitivity, you could also react to traces of formaldehyde or other chemicals used in the process.

2. If you have had a previous severe reaction to an influenza shot, you should consult your doctor before receiving another! The cause of the reaction should be determined if at all possible, so that you know whether you are allergic to one of the components of the vaccine or if you need to avoid immunizations for another reason.

3. If a child is less than 6 months old, the flu shot is not recommended. Children at this age are receiving a host of immunizations; some experts do express concern over the number and frequency of vaccinations for young children. There is also evidence that infant immunization is related to asthma development. Current research shows that rates of asthma are lower when immunizations are delayed.

4. If you have been diagnosed with Guillain-Barre Syndrome (GBS) at any time within 6 weeks of a previous flu shot, you should definitely consult with a doctor. The best advice currently rests on the fact that GBS is an autoimmune disease and vaccinations stimulate the immune system. Caution appears to be the order of the day with vaccinations after any episode of GBS.

5. If you are currently sick or running a fever, you should definitely wait until you are completely healthy before receiving an influenza immunization. Let your immune system finish its work before adding anything else for it to deal with.

Source: US News & World Report with additional research from Be Allergy Wise