Your son is experiencing recurring angioedema (swelling). Since it returns every few days, using antihistamines like Cetirizine only when symptoms appear is not enough to control it. He needs a proper evaluation by a pediatrician or allergist to identify the underlying cause, such as chronic hives or an allergen trigger. Please do not start new medications without professional advice. A doctor may prescribe a daily, preventative antihistamine plan rather than treating it reactively. Note: If he ever experiences difficulty breathing, throat tightness, or trouble swallowing, seek emergency medical care immediately.