evidence: All vaccine ingredients are present in very small quantities, and there is no evidence that they cause harm in these amounts. The exception to this is the small number of people who may be severely allergic to a vaccine ingredient, even if it is present only in trace amounts (for example, egg proteins or antibiotics used in vaccine manufacture). If you look up some vaccine ingredients on the internet you may read that they could be harmful, but most of them are present in vaccines in amounts that are completely normal for our bodies. Even common salt (sodium chloride), which is essential for the normal functioning of the body, is harmful in large quantities. [...] In the past, people with an egg allergy were advised not to receive the MMR vaccine. Advice on this changed more than ten years ago. The measles and mumps viruses are grown on a culture which contains chick embryo cells (not on eggs). This means that there is not enough egg protein in the MMR vaccine to cause allergic reactions, so children with severe egg allergies can safely receive the MMR. Doctors have carefully studied this issue and confirmed that there is no increased risk of reactions to the MMR vaccine in children who are allergic to eggs. See the video about this on the MMR vaccine page under 'Ingredients'.