Why do vaccines cause allergic reactions?

People can technically be allergic to anything and vaccines have multiple ingredients, so if a person is allergic to one of those ingredients, they will be allergic to the vaccine... just like any other vaccine, food, etc. 

Define 'allergic reaction.'

Anyone can be allergic to any of the ingredients in a vaccine.

What many people label as an allergic reaction are not that at all. Soreness at the injection site and general feelings of ill health for a day or two are part of the normal process of the patient developing the antibodies needed to fight the disease. When I told my doctor about my experience with the shingles vaccine, she said it was perfectly normal and a sign the vaccine was doing exactly what it was designed to do.

Because it's a Government conspiracy to make you allergic to everything and no immunities.

At the point when I used to offer influenza chances, I needed to inquire as to whether they were hypersensitive to eggs. The seasonal infection was brooded in egg whites prior to being bundled in vials for circulation. I needed to have epinephrine convenient in the event that they had a hypersensitive response to influenza shot.

It's bcuz of how they're processed. Like all injectable meds, they're produced in a carrier fluid that contains stabilizers, enzymes & preservatives for shelf life. So a person can be sensitive to one of those chemicals or in combination, they can trigger an allergic reaction.

Nothing is incubated in aggs anymore, although they were. But people can be allergic to any number of known or unknown substances that trigger various allergic pathways and cellular products like histamine. The allergic pathways, there are several, are complex.

When I used to give flu shots, I had to ask the patients if they were allergic to eggs. The flu virus was incubated in egg whites before being packaged in vials for distribution. I had to have epinephrine handy in case they had an allergic reaction to the flu shot.

Because some vaccines contain traces of things some people are allergic to.

E.g. some vaccines are grown in a medium that contains egg. These vaccines can trigger people with egg allergies.