The disorder is most commonly part of a virus infection of the upper respiratory tract such as the COMMON COLD, INFLUENZA or infectious MONONUCLEOSIS, in which case the inflammation usually subsides as other symptoms develop. It may also be caused by a bacterium, most commonly the β-haemolytic STREPTOCOCCUS. In the developing world it may be the presenting feature of DIPHTHERIA, a disease now virtually non-existent in the West since the introduction of IMMUNISATION.

The onset is usually fairly sudden with pain on swallowing, fever and malaise. On examination, the tonsils are engorged, red and may be covered with a whitish discharge (PUS). This may occur at scattered areas over the tonsillar crypts (follicular tonsillitis), or it may be more extensive. The glands under the jaw are enlarged and tender, and there may be pain in the ear on the affected side: although usually referred pain, this may indicate spread of the infection up the Eustachian tube to the ear, particularly in children. Occasionally an ABSCESS, or QUINSY, develops around the affected tonsil. Even experienced doctors may find it difficult to distinguish between viral and bacterial tonsillitis.

Most cases need no treatment beyond pain-killers and temperature reduction. Therefore, doctors often take a throat swab to assess whether there are bacteria present before prescribing antibiotics. PENICILLIN and ERYTHROMYCIN are the drugs of choice where beta-haemolytic streptococci are isolated, together with paracetamol (or aspirin in those aged over 20) and plenty of fluids. Removal of tonsils may be advised when the tonsils and adenoids are permanently so enlarged as to interfere with breathing; when the individual is subject to recurrent attacks of acute tonsillitis which are causing significant debility, absence from school or work on a regular basis (more than four times a year); or when there is evidence of a tumour of the tonsil. Recurrent sore throat not due to tonsillitis is unlikely to be helped by removing tonsils.