Severe complications are rare with timely antibiotics, but some—like a peritonsillar abscess—can require surgical drainage. Warning signs include severe throat pain, difficulty opening the mouth, drooling, muffled voice, or trouble swallowing. Rarely, rheumatic fever or heart involvement can occur, with signs such as persistent high fever, joint pain, fatigue, shortness of breath, or chest pain. Any sudden worsening of symptoms should prompt urgent medical attention.