Kounis syndrome is the concurrence of acute coronary syndrome or coronary vasospasm with conditions associated with the release of inflammatory cytokines through mast cell activation in the setting of allergic or anaphylactic reactions. Many identified triggers have been identified in paediatric patients including exposures, drugs, and immunisations; however, to our knowledge this is the first case report of Kounis syndrome linked to immunotherapy. We present a case of a 9-year-old with seasonal allergies presenting with clinical symptoms of Kounis syndrome following her weekly subcutaneous injection of allergens. Clinicians need a high index of suspicion for Kounis syndrome in patients who develop systemic signs of anaphylaxis with clinical, laboratory, electrocardiographic, and echocardiographic findings of acute coronary syndrome to help direct therapy and improve outcomes.