If you or your child could have an egg-induced vaccine allergy, figure out where you fall on the color-coded system, and take steps from there.

The use of eggs to produce flu vaccine means problems for some people with egg allergies.

RODALE NEWS, EMMAUS, PA—If you're one of the millions of people living with a food allergy, or more likely, you're raising a child with one, you've probably wondered if it's OK to get the swine-flu vaccine. That's because seasonal and H1N1 vaccines are produced in the same way, using eggs, a common food allergen among children, to grow the virus in labs. But because egg sensitivity in people ranges from a mild skin irritation to life-threatening anaphylactic shock, it's not always clear if a vaccine containing trace amounts of egg protein could do more harm than good. However, a new color-coded rating system aims to simplify the issue. "On the one hand, we are concerned about the devastating effects of the new strain of flu, and on the other, we aren't sure if a history of egg sensitivity is enough to disallow the shot or spray," said Bobby Q. Lanier, MD, clinical professor of pediatrics at the University of North Texas HSC in Fort Worth and executive medical director of the American College of Allergy, Asthma & Immunology (ACAAI). "It is the consensus of most allergists that flu shots can be given to virtually every patient who needs them if the proper procedure is followed."

THE DETAILS: According to new guidelines adopted by the ACAAI, the American Academy of Allergy, Asthma and Immunology, and the Joint Council of Allergy, Asthma, and Immunology, if you've suffered an apparent allergic reaction after an immunization in the past, you should investigate the cause instead of avoiding all future vaccines. Out of the 235 million doses of vaccines given in the U.S. every year, about one dose per million causes anaphylaxis, a serious medical reaction in which it becomes hard to breatheand that can cause people go into shock.

While the egg allergy is a pain in the neck for some people seeking the flu vaccine, without the use of eggs in vaccine production, things would be much more complicated—and messy. Considered a breakthrough when this new technology emerged in 1931, viruses are still being grown in fertilized chicken eggs today. Before that, doctors would transfuse blood from a flu survivor to a person with symptoms, far less practical than a shot. Today, nearly all of the egg-source allergy-inducing protein is removed from the vaccine, but trace amounts can still be present, causing an allergic reaction in some people. To help classify risk, Amal Assa'ad, MD, professor at Cincinnati Children's Hospital Medical Center and vice chair of the ACAAI Adverse Reactions Foods Committee, recently unveiled a color-coded system. The levels pertain to both children and adults, although egg allergies are more common in children—it's the second most common food allergy of children (behind milk), but kids often grow out of this allergy by the time they are 5 years old.