Hay fever is inflammation of the lining of your nose, eyes, throat and sinuses due to an allergy. When cells in these areas come into contact with an allergen, they release histamine, which causes inflammation.
Most often this response is triggered by grass pollen. Other allergens that can cause hay fever, include:
- house dust mites
- mould spores
- hair and skin flakes from animals (also known as ‘dander')
- cockroach droppings.
Hay fever is also known as allergic rhinitis, which has 2 types:
- Seasonal allergic rhinitis – when symptoms happen at certain times of the year, eg, spring. Wind-borne pollens are the cause of seasonal hay fever, which usually occurs in spring and summer. The length of the pollen season depends on where you live and the plant species you are allergic to.
- Perennial allergic rhinitis – when symptoms occur at any time of the year. Dust mites and domestic pets are the most common causes of perennial rhinitis.