Muscle aches and stiffness may occur following the flu vaccine, but are not cause for alarm and generally dissipate within two days. Signs of an allergic reaction to the flu vaccine include hives, trouble breathing, fast heartbeat, dizziness and weakness, states Healthline. Patients with these symptoms should seek immediate medical care.
Severe allergic reactions to the flu vaccine are rare, according to Healthline. They typically appear within a few hours of receiving the vaccine. Patients who are allergic to chicken eggs should not get the flu vaccine, since it is made from chicken eggs. Those who have previously suffered an allergic reaction to a vaccine should also avoid the flu shot.
There are many side effects associated with the flu vaccine but most are mild, according to Healthline. Some patients experience headaches after vaccination by injection or nasal spray. Headaches are considered a mild side effect, and tend to last two days or less. A low-grade fever below 101 degrees Fahrenheit is also common and is not a cause for alarm, though patients with fevers above 101 degrees F should seek medical attention. The most common side effect of the flu vaccine is soreness or pain at the injection site. The nasal spray form of the vaccine may also cause a runny nose or sore throat.