Allergic Reactions to the Flu Vaccine

Knowing the Signs and When to Act Fast

Some side effects are common with flu vaccines, while others are less so. Most of these—soreness, low-grade fever, for example—don't preclude you from getting the flu vaccine, however. One of the only exceptions is a true allergy to the flu vaccine itself—namely, the egg proteins that many versions contain.

Flu vaccines are recommended for nearly everyone. Unfortunately, many people opt not to be vaccinated for a variety of reasons, including everything from misinformation about flu shot efficacy to concerns about possible health risks.

It is important, therefore, to understand what a true allergy is and what your risk of an allergic reaction to a flu shot or flu nasal vaccine is before deciding to forego one. Flu shots aren't perfect, but they are they offer the best protection against influenza and its potential complications.

Side Effects of the Flu Vaccine

Some people will experience reactions to flu vaccination. Most of these side effects are mild and tend to resolve on their own within a day or two. The flu vaccine does not cause flu.

Side effects of the flu shot include:

  • Pain, swelling, or redness at the injection site
  • Low-grade fever
  • Minor body aches
  • Headache
  • Nausea

Side effects of the nasal flu vaccine (FluMist) include:

  • Runny nose
  • Wheezing
  • Headache
  • Vomiting
  • Muscle aches
  • Fever
  • Sore throat
  • Cough

While there is a possibility of an allergic reaction to either type of flu vaccine, the actual incidence of flu vaccine allergy is low, affecting only one or two people out of every million doses, according to the Centers for Disease Control and Prevention (CDC).

Allergic Reaction Causes and Risk Factors

A true allergy is one in which the immune system produces defensive antibodies against a substance that is otherwise harmless. This differs from a drug sensitivity in which there is a reaction but no production of antibodies.

An allergy to the flu vaccine is concerning because it can lead to a potentially life-threatening allergy known as anaphylaxis. The main trigger for this severe reaction, surprisingly, is egg.

FluMist and most flu shots are manufactured using egg-based technology. Because of this, they contain trace amounts of egg proteins called ovalbumin, which 1.3% of children and 0.2% of adults are allergic to.

Risks vs. Benefits

Just because you have an egg allergy doesn't mean you are destined to have an allergic reaction to FluMist or a flu shot. According to the American Academy of Allergy, Asthma, and Immunology (AAAAI), even those with a confirmed egg allergy can safely receive the vaccines. The benefits of flu vaccination almost universally outweigh the potential risks. In fact, the AAAAI states that it is no longer necessary to even ask about egg allergy prior to giving or receiving the flu vaccine.

Signs of a Vaccine Allergy

Because an allergic reaction to the flu vaccine is so rare, it is more important to recognize the signs of an allergy than to avoid vaccination.

If an allergy occurs after vaccination, it should be treated as a matter of urgency no matter how mild the symptoms are. This is because anaphylaxis can often strike quickly. In other cases, the initial symptoms may appear to resolve only to re-emerge with a second, stronger (biphasic) reaction one to 12 hours later.

Call 911 or seek emergency care if you experience any of the following after flu vaccination:

  • Rash or hives
  • Shortness of breath
  • Wheezing
  • Rapid heartbeat
  • Nausea and vomiting
  • Swelling of the lips, face, tongue, or throat
  • Dizziness and/or fainting
  • Confusion
  • A feeling of impending doom

If not treated immediately, anaphylaxis can lead to shock, coma, asphyxiation, heart or respiratory failure, or death.

A small rash at the injection site is not considered a severe allergic reaction. Soreness at the injection site is normal and should resolve within a day or two.

A Reaction That Isn't an Allergy

Even if you don't have a true allergy to the flu vaccine, you may experience a reaction that is serious enough to warrant avoidance of the vaccine in the future.

Guillain-Barré syndrome (GBS) is an autoimmune disorder affecting the nerves that can sometimes be triggered by the flu vaccine. It is extremely rare and occurs more commonly after a respiratory or gastrointestinal illness than it does following vaccination.

GBS typically begins with weakness, pain, or tingling in the feet or legs (especially in children). After these initial symptoms calm or disappear, serious long-term symptoms may suddenly develop, including weakness on both sides of the body. In some cases, the weakness will migrate from the upper to the lower body.

Symptoms of GBS at this stage include:

  • Loss of coordination and unsteadiness
  • Difficulting speaking, swallowing, or chewing
  • Difficulty with eye muscle control
  • Vision problems
  • Difficulty breathing
  • Irregular heartbeat
  • Severe neuropathic pain, especially at night
  • Digestion problems
  • Loss of bladder control

Even though most people with GBS fully recover, it can take a long time and may, in some cases, result in permanent muscle weakness or paralysis. If you've had GBS after previous flu vaccination, speak with your doctor or a rheumatologist to find what other options may be to you.

What You Can Do

If you have a known egg allergy and have experienced severe symptoms in the past, talk to your doctor about two egg-free flu shots approved by the FDA:

  • Flublok quadrivalent (for use in adults 18 years and older)
  • Flucelvax quadrivalent (for use in people 4 years and older)

With that said, any severe allergic reaction to a flu vaccine, whether it contained egg albumin or not, is a contraindication for future use.

If you've had an adverse reaction following a vaccination, report it to the Vaccine Adverse Event Reporting System (VAERS). This not only provides the CDC with valuable information to ensure future vaccine safety, but it is also the first step toward formally recording the incidence if you decide to file a claim.

Claims can be filed with the National Vaccine Injury Compensation Program, a no-fault initiative that allow you to resolve vaccine injury cases without the cost of legal representation. Even if a finding isn't made, you may still be eligible to receive financial compensation through a settlement.

A Word From Verywell

True allergic reactions to flu vaccines are extremely rare, and the potential risk should not deter you from getting the vaccine. However, if you experience adverse symptoms of any kind, contact a healthcare provider to seek the proper treatment.

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Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Flu vaccine and people with egg allergies. November 25, 2019.

  2. American Academy of Allergy, Asthma, and Immunology. Egg allergy and the flu vaccine. August 19, 2019.

  3. Pourmand A, Robinson C, Syed W, Mazer-Amirshari M. Biphasic anaphylaxis: A review of the literature and implications for emergency management. Am J Emer Med. 2018 Aug;36(8):1480-5. doi:10.1016/j.ajem.2018.05.009

  4. Winer JB. An update in Guillain-Barré syndromeAutoimmune Dis. 2014;2014:793024. doi:10.1155/2014/793024

  5. Health Resources & Services Administration. National Vaccine Injury Compensation Program. 2020.

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