By Dr Ananya Mandal, MD
The tonsils are small glandular structures located on either side of the back of the throat that provide a first line of defence against microbes. Most viruses and bacteria gain entry into the body via the nose and mouth. Healthy tonsils filter out these bacteria and also produce defensive immune cells against the invading microbes.
These defensive blood cells or macrophages present in the tonsils engulf the infective organisms and secrete digestive enzymes that destroy them. If the infection is serious, this can lead to pain and inflammatory changes such as redness, soreness and fever. Fever is actually a sign that the body's immune defences have been activated.
Tonsillitis or inflammation of the tonsils is usually caused by viral infection. The tonsils proper may be affected or the throat and surrounding areas including the back of the throat or the pharynx may be involved. It is rare for bacterial infections to cause tonsillitis. One of the most commonly feared bacterial causes of tonsillitis is infection with Group A streptococcal bacteria, which can result in strep throat.
Of the viruses, the most common cause of tonsillitis is adenovirus or the common cold virus. Another common viral infection is influenza. Other viruses that cause tonsillitis include rhinovirus (also causes the common cold), parainfluenza virus, enteroviruses (cause hand, foot and mouth disease), adenoviruses (cause diarrhoea), the measles virus and Epstein-Barr virus (causes glandular fever).
Tonsillitis may also be caused by an over-reactive and aberrant response of the immune system to the normal bacterial environment in the mouth and the throat. This is the reason why some people are more prone to tonsillitis than others.
Reviewed by Sally Robertson, BSc