What Are the Signs of an Allergic Reaction to a Vaccination?

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  • Written By: Alex Tree
  • Edited By: Melissa Wiley
  • Last Modified Date: 22 October 2018
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Having an allergic reaction to a vaccination is rare, but some people experience dizziness, hives, or breathing problems. Dizziness is usually mild and does not require a doctor’s attention. Hives are also rarely a serious allergic reaction, unless they persist for weeks or seem particularly severe. Difficulty breathing is an allergic reaction that should be responded to as soon as possible, preferably seeking emergency medical treatment. In addition, vaccinations can have a lot of negative effects on the body that are not allergic reactions at all.

The odds of having an allergic reaction to most common vaccinations are as unlikely as one in more than a million. If a person has a true allergy, the signs of an allergic reaction to a vaccination should present themselves within minutes of the injection. In rare cases, an allergic reaction occurs many hours after being exposed to an allergen. One of the most common allergic reactions is hives, which are red welts that grow and spread over the body. Hives can be itchy and painful, but they are usually harmless and go away within hours.


Dizziness or light-headedness is often categorized as a moderate to severe allergic reaction. If the dizziness is mild, the doctor who administered the vaccination should be alerted. He or she will usually recommend an over-the-counter medication and rest. If the dizziness is severe, emergency medical services should be contacted. It is important to remain calm during severe allergic reactions to lessen the chance of worsening the reaction.

Difficulty breathing is another severe allergic reaction that can occur after administering a vaccine. Raspy breathing and talking in a hoarse whisper are signs of breathing problems, which could be an allergic reaction to a vaccination. Emergency medical services should be contacted immediately. Having the person lie flat without a pillow can help open the airways and allow him or her to breathe more easily until help arrives. It may be necessary to perform cardiopulmonary resuscitation (CPR) and rescue breathing if the problem becomes worse.

Although having an allergic reaction to a vaccination is rare, many people experience side effects. Pain at the injection site, fever, and signs of the common cold are frequently observed. The type of side effects usually depends on the vaccination; for example, signs of the common cold are typically seen in people who are given an influenza vaccination. These side effects are generally mild, but they are not allergic reactions, nor should they be treated as such.



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