Acute tonsillitis may be defined as inflammation of the tonsils, predominantly due to infection. It is part of the spectrum of pharyngitis, which ranges from localised tonsillar infection to generalised infection of the pharynx and commonly affects young healthy adults. Simple sore throats secondary to viral or bacterial pharyngitis are very common and generally do not require hospital admission or antimicrobial treatment. Supportive management in the form of analgesia and adequate hydration is often sufficient. However, there is potential for life-threatening complications to develop, highlighting the need for basic knowledge in the management of these conditions. This article aims to provide an overview of acute tonsillitis and its complications, including peritonsillar and parapharyngeal abscess formation. Specific attention will be given to the pathogenesis, diagnosis, investigation and management of each condition, in particular advising on emergency pre-shore treatment and indications for referral to an Ear, Nose and Throat Department. We will also summarise important guidelines and evidence from the literature to support these management decisions.