Allergy and hayfever fast facts
What is an allergy?
An allergy occurs when your body becomes hypersensitive to a particular substance (known as an allergen) found in your surroundings. Whenever the substance is breathed in, ingested or comes into
contact with your skin, your immune system overreacts and you experience symptoms such as a skin rash, swelling and itching.1
How does the body react?
Allergens cause the body to release large amounts of a chemical called histamine. Histamine causes the tissues in the body to swell, leading to the symptoms of allergies.2 Many allergy medications work by reducing the amount of histamine produced during an allergic reaction, hence the name “antihistamines”.
Symptoms of allergies and hayfever
Allergy symptoms can vary widely from person to person and can often depend on the substance causing them. An allergic reaction to pollen in the air, commonly known as hayfever, causes symptoms such as itchy, watery eyes, a sore throat, sneezing and a runny nose.3 Allergies affecting the skin may cause an itchy rash and localized swellings, known as hives.4 Read more about the symptoms of allergies.