WHAT CAUSES ALLERGIC RHINITIS?

Allergic rhinitis is a reaction to small particles in the atmosphere such as pollen.

When these particles come into contact with the lining of the nose of a susceptible person, they trigger an immune response in the nose lining, and this causes the symptoms of allergic rhinitis.

This process is known as an allergic reaction, and the particles that cause it are termed allergens. It happens when the immune system, which is designed to stop invasion by foreign bodies such as bacteria, mounts an inappropriately strong response to harmless substances. This over-reaction by the immune system is what distinguishes individuals with allergy from healthy persons.

There are many ways of reducing the symptoms of allergic rhinitis and these are listed below. You should discuss your symptoms with your doctor who can advise you on which treatments would be best for you.

ALLERGEN AVOIDANCE
The simplest treatment for allergic rhinitis is to avoid the allergen that causes your disease. This should be tried before taking medication, and may reduce symptoms to a level where they are no longer troublesome.

It may require some effort to avoid a particular allergen, so it is essential that you find out exactly which allergens cause your disease. A technique known as skin-prick testing can quickly and easily show which allergens you are sensitive to. If you have not had this done, your doctor should be able to arrange it.

• Drug treatment: the main treatments are antihistamines, corticosteroids, cromones, and decongestants. Which one you need depends on the severity of your disease, your age, and the type of allergic rhinitis you suffer from. Many are available from your local pharmacy, but some may need a prescription from your doctor

• Immunotherapy is given to people with severe disease who cannot use drug treatments. To get immunotherapy, you will probably have to visit an allergy specialist

  HOW DOES IMMUNOTHERAPY WORK?
  Allergic rhinitis is caused by an immune response to a foreign body allergen.

  Immunotherapy causes complex changes to the body’s immune system that prevents or reduces this immune response. For example, allergens are recognised by your body by components of the immune system called antibodies. These start the body’s immune response against the allergen. In people with seasonal allergic rhinitis, the level of antibodies in the nose rises during the pollen season, and returns to normal when the season ends. Allergen immunotherapy can reduce this seasonal rise in antibodies

During immunotherapy, you receive small doses of the allergen that induces your allergic rhinitis. As a result, you become desensitised to this allergen. This means that when you encounter the allergen naturally, your allergic response is reduced.

Research suggests that using immunotherapy against one allergen may prevent people developing other allergies. This might be particularly useful in children, as allergies tend to develop early in life. Recent studies have indicated that immunotherapy may prevent the development of asthma in children with allergic rhinitis.

• Alternative medicine: these are natural remedies that are available from your local pharmacy, health food shop, or from specialists. Most alternative medicines are not proven to improve allergic rhinitis

Click here for more information on alternative therapies.

Please see the Hayfever page for additional info

HOW DO ANTIHISTAMINES WORK?
Histamine is a chemical that causes many of the symptoms of allergic rhinitis: a runny nose, sneezing, itchiness of the nose, and a blocked nose. Histamine is found naturally in the body, but the amount of it increases during allergic reactions.

Antihistamines prevent histamine from causing these symptoms. Antihistamines block receptors to which histamine would normally attach to and initiate an allergic reaction.
As a result, sneezing, itchiness of the nose and eyes, and a runny nose are reduced. Antihistamines are less good at clearing a blocked nose. They also reduce itchiness of the eyes in people with rhinoconjunctivitis.

CORTICOSTEROIDS
There are two ways in which corticosteroids can be taken:

• Topical corticosteroids are applied directly to the nose using pump sprays or dry powder
• Systemic corticosteroids are given by mouth or by injection

Both topical and systemic corticosteroids are effective at treating allergic rhinitis, but topical corticosteroids are most commonly used because they are safer.

HOW DO DECONGESTANTS WORK?
A blocked nose is the result of increased blood flow to the lining of the nose. This causes swelling and reduces the space through which air can pass. A runny nose also reduces air flow through the nose.

Decongestants cause blood vessels to become narrow by mimicking a chemical found in the body (norepinephrine) that naturally causes blood vessels to constrict.

The narrowing of blood vessels reduces the volume of blood reaching the nose lining. This reduces any swelling within the nose and provides a larger passage for air to flow through.

CROMONES
Cromones are taken as nose or eye solutions. They can be used to treat mild allergic rhinitis symptoms. They work by blocking the release of inflammatory substances that cause allergic rhinitis.

They are generally less effective than antihistamines and topical steroids. They also need to be applied regularly. However, cromones have virtually no side effects.

Cromones may be useful in people that cannot use antihistamines. When taken before the start of the pollen season, they may be helpful in reducing allergic symptoms during the pollen season.

WHO IS AFFECTED?

Allergic rhinitis is the most common allergic disease.

• 10% of people may have seasonal allergic rhinitis

• 10–20% of people may have perennial allergic rhinitis

• In the US, 20–40 million people may have allergic rhinitis

Allergic rhinitis is more common in children.

• 20% of children with allergic rhinitis develop their symptoms by 2–3 years of age, and 40% develop symptoms by 6 years of age

The number of people affected by allergic rhinitis is increasing.

• The reason for the increase is not clear, but may be because of increasing levels of air pollution, rising dust mite numbers, less ventilation in houses and offices, dietary factors, sedentary lifestyles, and high hygiene standards that reduce exposure to natural microbes (the hygiene hypothesis)

• The number of children with allergic rhinitis has doubled in the last 20 years