A swollen and sore throat may be caused by a viral or bacterial infection, allergies, or irritation. You should rest, drink plenty of fluids, and take over-the-counter painkillers such as paracetamol. Gargling with warm salt water or using soothing lozenges can help relieve discomfort. See a doctor promptly if the swelling worsens, persists, or is accompanied by difficulty breathing or swallowing.