Hay fever, also known as seasonal allergic rhinitis. It is caused by an allergy to grass or hay pollens. The hay fever season generally begins with the release of pollen by trees. This may start as early as February and continue to late May. Trees such as birch and oak are particularly to blame.

Hay fever affects 15 to 20 % of the population in Britain, where it is mainly caused by grass pollen. In other countries other pollens cause major 'hay fever' as well; ragweed in the USA, birch tree pollen in Scandinavia, and cedar pollen in Japan, for example.

Causes

Anyone can get hay fever at any time in his life. If parents have allergies, their children are more likely to have allergies and more likely to experience hay fever.

Allergies are caused by an oversensitive immune system, leading to a misdirected immune response. The immune system normally protects the body against harmful substances such as bacteria and viruses. Allergy occurs when the immune system reacts to substances (allergens) that are generally harmless and in most people do not cause an immune response.

If you have hay fever, you may react to one or more common inhaled allergens. No matter what you're allergic to, the underlying cause of your misery is the same. During a process called sensitization, your immune system mistakenly identifies the allergen as an invader and produces an antibody against it called immunoglobulin E.

Symptoms

The main symptoms of hay fever are:

repeated sneezing attacks

Itchy or watery eyes

An itchy throat, palate and ears

Loss of concentration

A general feeling of being unwell (hence hay 'fever')

Runny nose

Congestion

Sneezing

Watery eyes

Roof of mouth itches

Cough

Severe symptoms may make sleeping difficult.

People who experience both asthma and hay fever may also wheeze and become short of breath.

Treatment

If you have eye allergies, try wearing wraparound or goggle-type sunglasses to protect your eyes from pollens. If you are exposed to pollen, wash your eyes and your eyeglasses frequently with soap and water. Use cool compresses to relieve eye symptoms. Ask your doctor about over-the-counter and prescription drugs that can provide relief.

If symptoms remain severe despite medication, you might benefit from desensitisation immunotherapy to grass pollen. You will be given injections of minute amounts of pollen over a three-year period to induce immune tolerance and cure the allergy. Unfortunately, this treatment is not widely available in the UK.

These oral medications and nasal sprays help relieve itching, sneezing and runny nose, but have less effect on congestion. They work by blocking histamine, an inflammatory chemical released by your immune system during an allergic reaction.