Hens' eggs are a common food in the American diet. They are consumed as a primary food source and added as an ingredient to other foods. In individuals who are hypersensitive to eggs, egg-containing foods can cause mild to severe allergic reactions if ingested. These individuals may also have adverse reactions to vaccines produced on egg media. Vaccines that are created on egg media include those for measles, mumps, and rubella; rabies; yellow fever; and influenza. The authors discuss recent developments in the use of egg-containing vaccines in hypersensitive patients.