Introduction
The flu vaccination can cause a number of side effects. Most of them are based on a local or systemic inflammatory reaction against the vaccine and last a maximum of two to three days. As a rule, they do not lead to longer-lasting complications.
More serious side effects are usually caused by allergies. These can be directed against various ingredients of the flu vaccine. Allergies can also manifest themselves as local reactions, in the worst case they can trigger an anaphylactic shock.
These are the typical side effects of an influenza vaccination
The typical side effects of an influenza vaccination are based on the local reaction of the body to the vaccination. This includes reddening of the injection site and swelling. Pain at the injection site and/or in the muscle into which the vaccination was injected is also not uncommon.
Diarrhoea can also be caused by a flu vaccination. If the entire body reacts to the vaccination, fatigue, exhaustion, fever and sometimes aching limbs may occur. Allergies to vaccine ingredients can also cause allergic reactions, up to and including severe life-threatening anaphylactic shock.
Redness
The redness after a flu vaccination usually occurs immediately at and around the injection site. It is based on a local immune reaction of the body against the flu vaccine. A particularly large number of immune cells are infiltrated into the area of the injection site, as there is a very high dose of the vaccine.
In order to get all the immune cells there, increased blood circulation is necessary. This increased blood flow is also noticeable in the superficial smallest blood vessels, so that a reddening of the skin occurs. The reddened area is usually also warmed up.
The overheating is also due to the immune reaction. The body thereby tries to reach a temperature that is harmful to the invading virus. This is intended to weaken it and facilitate the immune defence.
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