Hayfever, clinically known as seasonal allergic rhinitis is a type of allergy. The term hay fever is a misnomer: the condition is not caused by hay, nor does it produce fever.
What is hay fever?
Hay fever is an allergic reaction to small particles of plant or animal protein that weigh little enough to be carried through the air and get deposited on the membranes of the eyes, nose and throat. People get confused by the term hay fever is a misnomer since it is not caused by hay and also does not produce fever.
In some people, the immune system is overactive and identifies normally harmless particles as dangerous, producing an excessive reaction.
This reaction results in the release of powerful chemical agents, of which histamine is the best known. These substances cause very severe swelling of the mucous membrane lining the nasal passages and conjunctiva of the eyes. In addition, it causes intense itching, sneezing and the production of large amounts of watery mucus.
Revised and reviewed by Professor Sharon Kling, Clinical Unit Head, General Paediatrics, Intensivist at Tygerberg Hospital and Associate Professor, Department of Paediatrics and Child Health at Stellenbosch University. February 2015.