Hayfever (allergic rhinitis)
Hayfever, also called seasonal allergic rhinitis, is an allergic response to pollen (the male component of the plant reproductive system) or other microscopic substances that are present only at certain times of the year. Allergic rhinitis can also be perennial (year-round).
In the spring, pollinating trees are responsible for causing hayfever. Over the summer, grasses and weeds produce the pollen. And in autumn weeds are mostly to blame. Hayfever can also be caused by mould releasing its reproductive cells, called spores, from late March until November, usually peaking in late summer and early autumn.
Perennial allergic rhinitis is caused by agents that are present throughout the year, such as house dust mites, mould, animal dander and feathers. These irritants can be found in pillows, down clothing, curtains, upholstery, thick carpeting and bedding.
It is common for people to be allergic to more than one pollen or agent
What are the symptoms of allergic rhinitis?
Your body’s immune system interprets the allergen (such as pollen, mould, dander) as an ‘invader’ and responds by releasing a chemical called histamine into the bloodstream.
Histamine causes inflammation (swelling and redness) of the sinuses, nose and mucus membranes of the eyes, and triggers sneezing. The swelling reaction is designed to block the allergen from entering the body and sneezing is a method to expel it out of the body. Histamine also allows fluids to enter the nasal tissue, resulting in congestion, itching and a runny nose.
People with allergic rhinitis have sudden sneezing, a watery nasal discharge, puffy eyes and fatigue. Symptoms can occur at all stages of life, but most people develop allergic rhinitis before the age of 30.
How do I find out what causes my allergies?
The season in which your allergy occurs will narrow the list of possible culprits. To pinpoint the cause, your doctor may arrange for you to have a skin test to determine which substances (allergens) cause a reaction.
The skin test involves placing extracts of potential allergens in a grid on your arm or back, and then pricking your skin so the extract can enter the outer layer of skin (epidermis). Those areas that become red and itchy indicate which substances trigger a defensive (allergic) response by your immune system.
Your doctor may recommend a blood test to check the levels of antibodies produced by the immune system. Elevated levels of certain antibodies can identify particular allergies.
Why do only some people get seasonal allergies/hayfever?
Hayfever affects around one in five people in the UK, according to the NHS. It is unknown why some people get allergies while others do not. However, there is some evidence to suggest that hayfever and other types of allergies are hereditary (passed on from parents to children). People who suffer from asthma or eczema are also more likely to develop hayfever or perennial (year-round) allergic rhinitis.