Common side effects of the flu shot: what to expect


  • Side effects of the flu shot may include pain at the injection site, headache, and mild fever.
  • Side effects of nasal spray are runny nose, wheezing, sore throat, headache, and fever.
  • Allergic reactions are about one in a million, but breathing difficulties could indicate one.
  • Visit Insider’s Health Reference Library for more tips.


vaccine against influenza
has side effects like pain around the injection site and headaches, but these are short lived and should not deter you from getting the vaccine.

On rare occasions, the flu shot can trigger an allergic reaction that should be treated by a doctor.

Here’s what you need to know about the side effects of the flu shot and how to tell the difference between a normal reaction and an allergic reaction.

Common side effects of the flu shot

Some of the most common side effects flu shots include:

  • Pain, redness, small rash or swelling at the injection site
  • Headache
  • Mild fever (less than 101 ° F)
  • Nausea or upset stomach

Side effects usually start soon after the injection and should only lasts a few days, According to the CDC.

“Headache, fever, and muscle aches are not a sign of allergic reactions,” says Michael mcneil, MD MPH, Team Leader for Vaccine Safety Data Liaison at CDC Immunization Safety Office. “These reactions can occur as a result of the patient’s immune system response to a vaccine.”

Most of these side effects are inevitable, but to avoid arm pain try take ibuprofen two hours before you receive your vaccine.

Side effects of nasal spray

Getting a nasal spray flu shot can help you avoid some side effects of the flu shot, such as arm pain, but it comes with its share of side effects.

Possible side effects nasal spray vaccine include:

  • Runny nose
  • wheezing
  • Sore throat
  • Headache
  • Fever
  • Nausea

Nasal vaccines are safe for most people between the ages of 2 and 49, according to the CDC. But some groups who should not receive the nasal spray include:

  • People with weakened immune systems
  • Adults 50 years of age or older
  • Children 2-4 years of age who have had severe asthma in the past year
  • Children aged 2 to 17 who are taking medications such as therapies containing aspirin and salicylates
  • Pregnant women

Also, those who need to be very careful when receiving the nasal spray vaccine include:

  • People with asthma over 5 years old
  • People with lung disease, heart disease or diabetes
  • People who currently have an acute illness

Find a complete list of those who should avoid nasal spray and who should take precautions on the CDC website.

Allergic reactions to influenza vaccine

Although the side effects listed above are normal reactions to the flu vaccine, it is important to monitor your response to the vaccine to make sure you are not having an allergic reaction.

Although allergic reactions are rare – they occur in a 1.3 in 1 million vaccines – they can be serious.

Symptoms of a severe allergic reaction to a flu shot include:

  • Difficulty in breathing
  • Hoarseness or wheezing
  • Paleness / pallor
  • Weakness
  • Rapid heartbeat
  • Dizziness

According to McNeil, these symptoms usually occur “within minutes to hours of receiving the injection and require immediate medical evaluation and treatment.”

The flu shot, like all vaccines, contains several components that can cause an allergic reaction. Most allergic reactions are caused by an allergy to egg protein, gelatin, or other additives in the vaccine. Although the flu shot contains traces of eggs, research has shown that most people with mild egg allergies can receive flu shots.

Serious non-allergic reactions

In extremely rare cases, the influenza vaccine can trigger Guillain-Barré syndrome (GBS), a neurological disorder that causes paralysis.

He is felt that only one or two individuals develop GBS per 1 million people vaccinated. GBS can occur days or weeks after vaccination, and manifests as acute muscle weakness, difficulty controlling eye muscles, or difficulty swallowing.

Anyone with these symptoms should contact their doctor.

Insider takeaways

The flu shot – either as a shot or as a nasal spray – can cause side effects, including headache, fever, and nausea. However, it is still important to get the vaccine every year.

“Influenza vaccines have a good safety record,” says McNeil.

The flu is a dangerous disease, especially for young people, the elderly and people with weakened immune systems.

Getting the flu shot will reduce your chances of getting the disease yourself or of passing it on to vulnerable people. While there are potential side effects, they are minor and short-lived for most people and should not influence your plans to get a flu shot.

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