Flu shot allergy: what to know

A tender arm, mild redness, tiredness, or a brief fever can occur after vaccination and does not by itself prove an allergy. An allergic reaction may involve hives, facial or throat swelling, wheezing, breathing difficulty, dizziness, or collapse. Symptoms that begin soon after an injection deserve prompt attention, especially when several body systems are involved.

Tell the clinician exactly what happened, how soon it began, which product was used if known, and whether treatment was needed. A reaction to an egg, antibiotic, latex, or another medicine is not automatically the same as a reaction to a flu vaccine.

Do not arrange a repeat dose without discussing the previous event. Bring your vaccination record and any discharge or allergy-clinic information. The provider may review the ingredients, consider an alternative product, or recommend observation after vaccination. Read about the [Inactivated Vaccine](/materials/inactivated-vaccine/) and ask which product is planned.

If the past reaction was only a sore arm or mild short-lived symptoms, describe it rather than labelling it an allergy. Accurate details help the clinician make a safer decision.

Call emergency services for trouble breathing, swelling of the tongue or throat, widespread hives with faintness, sudden collapse, or rapidly worsening symptoms after vaccination. Sit or lie down while help is coming and follow any emergency action plan prescribed for you. A delayed local reaction can still be discussed with a clinician, but breathing or circulation symptoms are emergencies.

Ask whether the earlier episode fits an allergic reaction, whether allergy assessment is needed, which ingredients matter, and how you would be monitored if vaccination is recommended.