Signs of an allergic reaction to the flu shot can include:

• Difficulty breathing
• Hoarseness or wheezing
• Swelling around the eyes or lips
• Hives
• Paleness
• Weakness
• A fast heart beat or dizziness

These signs would most likely happen within a few minutes to a few hours after the vaccine is given. Life-threatening allergic reactions to the flu shot are rare, but if you experience any of these symptoms, it is important to seek medical attention immediately. It is also recommended to report any severe reactions to the Vaccine Adverse Event Reporting System (VAERS) .