Hay Fever Patient Information Fact Sheet

What is hay fever?
Hay fever is an allergic condition in which the body’s immune system overreacts to pollen and other substances that are otherwise harmless. The substances to which people are allergic are referred to as allergens. Hay fever is also known as seasonal allergic rhinitis (irritation and inflammation of the nasal lining). As the word “seasonal” suggests, the allergy usually occurs at specific times of the year. Most people suffer from symptoms in the spring, summer or autumn depending on the cause of their allergy. There is a genetic predisposition to hay fever and allergies. The allergy tends to become active when a person has been exposed to the same irritant a number of times.

What are the symptoms of hay fever?
The main symptoms of hay fever are a runny nose, nasal congestion, sneezing, coughing, itching of the nose and eyes, and watery eyes. Loss of smell is common and can affect the sense of taste. The eyes can become red and swollen causing difficulties with many activities. For people with extreme allergies, the symptoms may be severe enough to prevent them sleeping properly. The symptoms usually occur at specific times each year; many people start to suffer symptoms in the spring because of pollen in the air from spring flowers and trees.

What causes hay fever?
In most cases, hay fever is caused by an allergy to pollen from flowers, trees or grasses. Although pollen itself is not a harmful substance, the immune systems of people with hay fever react as if it is. In these people, contact with pollen (or other allergens) causes their body to produce excessive amounts of a substance called histamine. This leads to inflammation of the mucous membranes that line the eyes, nose, and air passages. Many people are allergic to more than one substance. Molds—such as those on leaves—may also act as an allergen. Ideally, knowing the exact substance that is causing their allergy should allow sufferers to avoid contact with that substance. However, this is often impossible, particularly if the allergen is pollen in the air. Allergies in children may change and develop with age as they become exposed to other irritants.

What tests confirm a diagnosis of hay fever?
Skin testing is the only way to identify allergies to different substances. Once the allergen is known, the hay fever sufferer can then try to minimize their exposure to it where possible. One type of skin test involves small amounts of different solutions of pollens and allergens from various sources being placed on the skin. The skin is then pricked to allow the solution to enter under the skin surface. This test causes minimal discomfort and is suitable for children. Redness and swelling will occur if there is an allergy to a substance.

An allergy blood test, sometimes called the radioallergosorbent test (RAST), can assess your immune system’s response to a specific allergen by measuring the amount of immunoglobulin E (IgE) antibodies. A blood sample can be sent to a lab, where it can be tested for evidence of sensitivity to possible allergens.

Keeping a history of allergic reactions can also be useful as some reactions happen immediately on exposure to an irritant substance. However, other reactions may occur up to 24 hours later, making the cause harder to identify.