Influenza, or the flu, is a viral respiratory infection that can lead to serious complications, particularly in young children, the elderly and individuals with other respiratory diseases or weakened immune systems. The flu shot offers protection against certain strains of the influenza virus. The Centers for Disease Control and Prevention advises that individuals over the age of 6 months be vaccinated against the flu annually. Severe allergic reactions to the flu shot are rare but can occur in some individuals and require urgent medical treatment.
Minor Allergic Reaction
A minor local reaction can occur at the site of injection of a flu vaccine, causing swelling, redness, soreness and pain. These mild symptoms are common among children and usually subside within 48 hours. MayoClinic.com notes that some individuals may also experience a temporary systemic reaction that affects the whole body. Fever, muscle aches and fatigue may occur a few hours after getting a flu shot and normally last for 24 to 48 hours.
Serious Allergic Reaction
Symptoms of a serious allergic reaction that require immediate medical attention include difficulty breathing, wheezing, hoarseness, paleness, weakness, dizziness, a rapid heart beat and hives or a rash on the skin. A severe egg allergy can cause a reaction after a flu shot because influenza vaccines are incubated in chicken eggs. Any individual who is allergic to eggs or has had an allergic reaction to a flu shot in the past should consult a doctor before getting the flu vaccine.
Guillain-Barre Syndrome
The CDC cites Guillain-Barre Syndrome as a condition that is associated with an adverse reaction to the flu vaccine. This illness is characterized by symptoms such as fever, nerve damage and muscle weakness. According to the CDC, studies suggest that the risk of developing Guillain-Barre Syndrome due to the flu shot is a one in a million.
