Side effects of the flu shot are usually mild and only last one to two days. The most common one is soreness or swelling at the injection site. Experts typically recommend a yearly shot unless you have certain allergies.

Every year, people protect themselves from influenza, or the flu, by getting the flu vaccine. This vaccine, which typically comes as a shot or nasal spray, can reduce your chances of having to go to the doctor because of the flu by as much as 60 percent.

Most side effects from the flu shot are typically mild. However, in rare cases, they can be severe. Before you get your flu shot, you may want to know what to expect.

A mercury-based preservative called thimerosal is used in some multidose vials of the flu vaccine. It’s used to prevent bacteria and other germs from growing. According to the Centers for Disease Control and Prevention (CDC), thimerosal use in vaccines is safe and causes few side effects.

If you’re concerned about thimerosal, you can ask for a vaccine that doesn’t contain it.

The more common side effects of the flu shot are mild. They’re the same in adults and children.

Reaction at the injection site

The most common side effect of the flu shot is a reaction at the injection site, which is typically on the upper arm. After the shot is given, you may have soreness, warmth, and in some cases, slight swelling. These effects usually last less than two days.

Headache and other aches and pains

After your shot, you may experience headaches or body aches. This also usually happens on the first day and goes away within two days. Taking pain relievers can help ease your discomfort.

It’s controversial whether it’s safe to take acetaminophen or ibuprofen to treat these vaccine side effects.

Some research suggests that these medications might change or decrease how your body responds to the vaccine.

Other research is mixed. It’s still unclear whether these medications should be avoided.

Dizziness or fainting

You may experience dizziness or fainting with the flu shot. These effects shouldn’t last longer than a day or two. If you tend to get dizzy or faint when getting a shot, be sure to tell the healthcare professional before they give you the flu shot.

You can also try:

  • sitting for a while after you receive the shot
  • having a snack before or after the shot

Q:

Does the nasal spray flu vaccine cause different side effects from the flu shot?

Anonymous reader

A:

Like the flu shot, the flu nasal spray — also called the live attenuated influenza vaccine (LAIV) — may cause headache, dizziness, fainting, and a slight fever. However, the nasal spray can also cause other side effects that the shot doesn’t, including tiredness, loss of appetite, runny nose, and sore throat. Please note, the nasal spray isn’t available every year. Check the CDC website for more information on the flu nasal spray.

Healthline Medical TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Rarely, the flu vaccine can cause a severe allergic reaction. Severe allergic reactions usually happen within a few hours of receiving the vaccine. Symptoms include:

If you have any of these symptoms, it is important to seek medical support immediately. If they’re severe, call 911 or go to the nearest emergency room.

Guillain-Barré syndrome (GBS)

In very rare cases, some people who have received the flu vaccine have experienced Guillain-Barré syndrome (GBS). GBS is a neurological condition that causes weakness and paralysis throughout your body. However, it’s not clear if the flu vaccine is the actual cause of GBS in these cases.

That said, having GBS in the past doesn’t always mean you can’t receive the flu vaccine. Talk with a doctor to find out if the flu vaccine is safe for you.

You should speak with a doctor right away if you have symptoms of GBS after receiving the flu shot.

The flu shot is typically recommended for everyone ages six months or older. Anyone at risk of serious complications from the flu should also receive the flu shot, which includes:

  • pregnant people
  • people ages 65 and older
  • people with chronic health conditions as well as their caregivers

The shot isn’t recommended for people who:

  • have had an allergic reaction to the flu shot in the past
  • have a severe allergy to eggs
  • are currently sick with a moderate to severe fever

The flu shot is a safe, effective treatment with few side effects. If you’re unsure of whether you should get the vaccine, you can talk with a doctor or pharmacist. They can help you decide if a flu shot is right for you.

Questions you may ask include:

  • Is getting a flu shot a good idea for me?
  • Which flu vaccine is best for me?
  • Am I at risk of serious complications from the flu?
  • Am I at high risk of side effects from the flu shot?

Q:

Can I get a flu shot if I’m allergic to eggs?

Anonymous reader

A:

Most flu vaccines are made using eggs, so the vaccine could cause a reaction in people with an egg allergy. In the past, the CDC advised many people with an egg allergy to avoid getting the flu vaccine. But now, the CDC says that most people with egg allergies can safely get the flu vaccine.

Whether you can receive the flu vaccine or not depends on how severe your egg allergy is. If you’ve only had hives as a reaction to eggs, you can get any flu vaccine that’s otherwise safe for you. If you’ve had other symptoms from eggs, such as swelling or lightheadedness, you should only get the flu vaccine from a healthcare professional who’s trained to handle an allergic response. If you have an egg allergy, talk with a doctor about getting a form of the vaccine that’s safe for you.

Healthline Medical TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Side effects of the flu shot are usually mild and only last one to two days. The most common one is soreness or swelling at the injection site.

Experts typically recommend a yearly shot unless you have certain allergies.

The flu shot is a safe, effective treatment with few side effects. If you’re unsure of whether you should get the vaccine, consider talking with a doctor or pharmacist. They can help you decide if a flu shot is right for you.