Itchy eyes, runny nose and constant sneezing are symptoms of this increasingly common condition. Dr. Lesley Hickin and Dr Chris Brown give advice on allergic rhinitis and its most common form, hay fever

What is allergic rhinitis?
Inflammation of the membrane lining the nasal cavity is known as rhinitis. It can affect people all year round (perennial rhinitis) or can be seasonal (usually called hay fever), occurring at a specific time of year.

To understand allergies you need to know a little about the immune system and how it works. Your immune system protects you from infection by producing antibodies that kill harmful organisms. When you have an allergy your immune system overreacts to substances that you eat, breathe or touch. Immune system cells are located in areas of the body where they are in the front line of attack when an allergen appears. These areas are the nasal cavity, including the tonsils, the lungs and the intestines.

Reducing your exposure to allergens may help prevent allergic reactions but this is not always practical, and various treatments are available to combat the problem.

Symptoms
The symptoms of allergic rhinitis appear soon after contact with the allergen. They tend to be worse with hay fever (pollen allergy). They include an itchy sensation in the nose and throat, frequent sneezing, a blocked runny nose and itchy red watery eyes (allergic conjunctivitis).

When symptoms are really bad you may feel as if you have a high temperature, hence the term hay fever. The impact of hay fever on quality of life can be enormous, with most sufferers putting the symptoms themselves at the top of the list. Poor sleep (probably from nasal blockage) can cause sleep deprivation, daytime tiredness and irritability. Young people particularly complain of problems in concentration - unfortunately at the time of year when many are studying and taking exams.

Diagnosis
Allergic rhinitis is usually easy to diagnose from the description of the symptoms, particularly if you can identify the trigger factor from the pattern of your symptoms. For example, do you sneeze when there is a cat in the room? Does your nose always run when you empty the vacuum cleaner bag?

If the cause is not clear, you might be sent to an allergy clinic where you can have skin prick tests and blood tests to try to identify the cause. However, these are not done routinely because the results can be confusing. Sometimes no obvious cause is found.

Skin prick tests are simple and painless tests to find out which substances (allergens) cause allergic reactions in affected people. Dilute solutions are made from extracts of common allergens such as pollen, dust, animal dander (shed skin flakes), food and house dust mite. A drop of the solution is placed on the skin, which is then pricked with a needle. The skin is observed for a reaction, which usually occurs within 30 minutes of the solution being applied.

The most common allergens involved in causing rhinitis are:

1. The house dust mite. This is a microscopic creature, which feeds on flakes of human skin and is present in every household, however clean, but is only a problem if you are allergic to it. It causes symptoms all year round.
2. Pollens, moulds, animal fur and dander are other common allergens that tend to cause seasonal and more localised problems.

All of these allergens have to be inhaled to cause a problem, and affect up to 40 per cent of the population.

Prevention

• Avoid keeping furry animals as pets if you are allergic to them.
• Replace pillows and quilts containing animal feathers with synthetic stuffing.
• To reduce house dust mite numbers remove dust-collecting items such as carpets and curtains, particularly in the bedroom. Vacuum and turn your mattress regularly, cover the mattress with a spongeable cover and wash bed linen regularly.
• Some people suggest placing soft toys in the freezer every six months to kill the house dust mites.
• To prevent the symptoms of hay fever avoid areas with long grass or where grass is being cut. In summer keep the doors and windows closed and spend as much time in air-conditioned buildings as possible. Try to stay indoors when the pollen count is highest, such as late morning and early evening. Keep the lawn mowed short to prevent grasses flowering.
• Wear sunglasses to avoid pollen getting in your eyes, and shower when you get home to remove pollen from your face and nose.
• To avoid moulds keep your house well-ventilated and free from damp.

Treatment
Antihistamine drugs (tablets or syrups) prevent symptoms such as itching, sneezing, and a runny nose. Many are available, both over the counter and on prescription. The most recently developed antihistamines such as Desloratidine and Fexofenadine are less sedating, and less likely to interact with other drugs than the older types of antihistamines.

Topical nasal steroid sprays such as Beconase and Nasonex are very effective if used correctly. They should be used according to the instructions in the pack and are most effective for hay fever if you start before the pollen season starts and continue until after the season finishes. The steroid is not absorbed into the bloodstream enough to give any side effects and so is safe for everyone.

Steroid injections are also available and will provide relief for up to six weeks. They are not used routinely because of the potential side effects of steroids, particularly in children.

Immunotherapy Immunotherapy attempts to alter the way a person reacts to an allergen and has been shown to be particularly effective for hay fever. There were concerns about the safety of this injected treatment, and in 1986 strict guidelines were laid down to restrict its use to specialised centres. The recent development of an oral 'vaccine' for hayfever, called Grazax may in the future bring safe immunotherapy to the masses. It needs to be taken daily, starting at least 4 months in advance of the hayfever season, and continued throughout the season, to be effective.

Who is affected?
There is a lot of evidence now to show that allergic conditions are getting more common. There are several plausible theories for this, for example, more house dust mites are found in houses with central heating, wall-to-wall carpeting and double glazing. Another theory is that as children are exposed to fewer childhood infections their immune systems become more active in other directions. Certainly the numbers of people with rhinitis, asthma and eczema are on the increase; it is estimated that by 2015, half the population of Europe will suffer some kind of allergy.