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Symptoms of Allergic Reactions to Flu Shot

Symptoms of Allergic Reactions to Flu Shot

Although the flu shot is mostly safe for all, some people tend to experience certain allergic reactions after getting it. This HealthHearty article explains the symptoms that will help you identify if you are allergic to flu shot or not, and if you should be concerned about getting it in the first place.
Bhakti Satalkar
Last Updated: Apr 9, 2018
Did You Know?
Centers for Disease Control and Prevention (CDC) recommends everyone who is six months of age and older to get a flu vaccine every season. In fact, depending upon a person's suitability for vaccination, various flu vaccines are available to ensure that the risks of developing any kind of allergy are minimized.

Seasonal flu vaccines are designed to protect us from the most common influenza viruses that thrive during seasonal changes. According to CDC, "For the 2014-2015 influenza season, trivalent and quadrivalent inactivated influenza vaccines (IIV) are available. The trivalent IIV is designed to protect against three influenza viruses - one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus. Quadrivalent IIV and live attenuated influenza vaccine (LAIV) contains the same three viruses as the trivalent vaccine, but also contains an additional influenza B virus."
Most influenza vaccines contain viruses that are grown in hens' eggs. In case of the flu shot, these viruses are inactivated or recombinant. The only vaccines that consists of live and weakened viruses are the ones that are available in the form of nasal sprays. Nonetheless, since this write-up is about the possible side effects associated with flu shots (injections), we shall be focusing on that aspect only.
Common Allergic Symptoms after Getting the Flu Shot
Like any medication, even this involves certain risks. Centers for Disease Control and Prevention states that the chances of having severe allergic reaction to any vaccine is less than 1 in a million doses. And that the symptoms for the same would be visible within a few minutes to a few hours after the vaccination has been taken. Normally, most people experience mild reactions at the site where the vaccine is injected. However, this is quite normal and the symptoms fade away within a day or two. Listed below are some commonly observed symptoms of flu-shot allergy.
Mild Symptoms
  • Redness
  • Swelling
  • Pain
  • Soreness
  • Fatigue
  • Itchiness
  • Headache
  • Rashes
  • Hoarseness

The occurrence of these symptoms is normal and they may be evident for a day or two. After that, they are likely to disappear on their own.
Moderate Symptoms
  • Fever
  • Redness, soreness, and itchiness in eyes
  • Cough
  • Body ache
  • Seizures

Children may experience seizures due to fever if the flu vaccine has been taken along with pneumococcal vaccine (PCV13), around the same time.
Severe Symptoms
  • Very high fever
  • Breathing difficulty
  • Accelerated heartbeat
  • Behavioral changes
  • Hives
  • Facial swelling
  • Swelling of throat
  • Weakness
  • Fainting spells

As mentioned earlier, in case of a severe reaction, the aforementioned symptoms will be visible within a few minutes to a few hours after the vaccination has been administered. It is strictly suggested to call 911 in case you experience any of these signs.
Many falsely believe that getting the flu shot also exposes one to flu viruses. Hence, they experience flu-like symptoms after getting it. We have already mentioned earlier that flu shots contain inactivated vaccine that has no live virus. Therefore, it is impossible to get flu after getting the shot. Having said that, it is important to note that it takes around two weeks for the vaccination to actually make the body immune to influenza. Therefore, if the body has been infected with the virus before getting vaccinated, or within that two-week period, then it is possible for one to be infected by flu. Alternately, there are many other infections and health conditions that have symptoms quite similar to that of flu, often leading to a false self diagnosis.
Who Are Likely to Experience Allergic Reactions
Those with severe egg allergy may experience allergic reactions to flu shots, as most of the vaccines contain egg protein. For such people, there is a flu vaccine that does not contain egg protein, and can be safely administered to those who are 18 years of age and above. However, Mayo Clinic states that in most cases, even those with egg allergy can be given a vaccine that contains egg proteins. Nonetheless, it is imperative to discuss this problem with your physician.
Other than egg allergy, those who have a history of experiencing allergic reactions after taking flu shots, or are allergic to any antibiotic, or are on continuous medication, etc., may experience a possible reaction due to the components of the vaccine.
Anyone with the history of 'Guillain-Barré Syndrome (GBS)'―a condition where the immune system ends up attacking the nerves of the body, eventually leading to paralysis―should not get this vaccine.
This vaccination should not be taken during an illness. Although it is considered okay to get this shot during mild illnesses, but doctors still suggest to wait for the body to recover completely and then proceed.
The risks associated with getting the flu shot are quite minimal when compared to the risks involved in not getting one. Therefore, before completely disregarding it as an option, it is highly recommended to speak with a trusted physician and openly discuss your medical history, age, physical health, medications and doses, allergies, etc. With so many types of flu vaccines available, each suitable for a different age group, or for specific allergies, your doctor would be able to help you chalk out the best option available for you.
Disclaimer: This HealthHearty article is meant for informational purposes only and should not be considered as a replacement for expert medical advice.