Varicella side effects: expected reactions and warning signs

A sore, red, or swollen injection site reflects local immune activity. Some people feel tired or develop a mild fever. A small rash may appear later and should be described to a clinician if it is extensive, painful, or accompanied by feeling very unwell. These reactions differ from chickenpox itself, which can cause crops of itchy, fluid-filled blisters. They also differ from shingles, which is a later reactivation of varicella in the body.

Rest, drink fluids, and avoid rubbing the injection site. Follow the vaccinator's instructions for symptom relief and check medicines carefully for age and health restrictions. Note when symptoms began, how they changed, and whether fever or blisters appeared. If the reaction is uncertain, contact a GP rather than assuming it is expected. Information on [Fever](/symptoms/fever/) and [Skin Blisters](/symptoms/skin-blisters/) can help you describe what you see.

Call emergency services for difficulty breathing, throat tightness, facial swelling, collapse, or widespread hives. Seek prompt medical advice for a severe headache, confusion, repeated vomiting, persistent fever, a rapidly spreading rash, or blisters near the eyes. A child who is difficult to wake, not drinking, or passing very little urine needs urgent assessment. A [GP Consultation](/treatments/consultations-and-assessment/gp-consultation/) can help when symptoms are worrying but not immediately life-threatening.

Ask which reactions fit the timing of your dose, what symptom-relief options are safe, and whether a future dose should be reviewed. Mention previous allergies, immune problems, pregnancy, and every medicine being taken.