Allergic rhinitis is inflammation of the nasal lining.
It causes chronic sneezing, runny nose or a blocked nose.
Seasonal allergic rhinitis is also known as hay fever.
It is caused by allergies to various types of pollen.
Perennial allergic rhinitis is caused by allergies to things like dust mites, chemicals and cats.
Skin prick tests can help identify what substance a sufferer is allergic to.
The rate of allergic rhinitis varies from 1.4 percent to 40 percent around the world.
There is evidence the prevalence of the condition is increasing.
What is allergic rhinitis?
Rhinitis means inflammation of the nasal lining or mucosa. It is characterised by chronic or recurrent sneezing, rhinorrhea (runny nose), itchy and blocked nose, which may be labeled as allergic when an allergen is identified. The most well known form of rhinitis is the common cold, which is infectious rhinitis due to a virus.
The hallmark of allergic rhinitis is the relationship of symptoms on exposure to an allergen. Your nose is not the only organ that may be affected in allergic rhinitis. You may have itching of your eyes (allergic conjunctivitis), throat and ears.
There are two types of allergic rhinitis:
Seasonal allergic rhinitis or hay fever - when symptoms are experienced only during spring and/or summer. It is usually due to various types of pollen, which are carried by the wind and easily breathed into the nose. When most people talk about hay fever it usually means seasonal allergic rhinitis.
Perennial allergic rhinitis - when symptoms are experienced all year round. It is usually caused by allergens such as house dust mite, particles from the family pets known as animal dander, or mould spores which are carried in the air.
Other causes of perennial rhinitis
Occupational: vets working with furred animals, bakers allergic to flour, health workers allergic to latex, etc.
Drugs: Oral contraceptives, hormone replacement therapy, aspirin & other nonsteroidal anti-inflammatory drugs and anti-hypertensives can all cause rhinitis.
How common is allergic rhinitis?
Allergic rhinitis is estimated to have a prevalence of up to 40% in the New Zealand and Australian populations.
A recent ISAAC study of 460,000 children aged 13 to 14 years found the prevalence of allergic rhinitis varies from 1.4 percent to 39.7 percent in countries around the world.
The lowest rates were found in parts of Eastern Europe, south and central Asia. The highest rates were found in regions in Canada, Australia, New Zealand, the United States and the United Kingdom.
The overall rate was 13.9 percent and nearly half of the children studied also asthma or eczema. Areas with low rates of allergic rhinitis also had low rates of asthma and eczema.
There is mounting evidence of a rise in the prevalence of allergic diseases, including rhinitis, over recent decades. Lifestyle factors may be important given the high prevalence of rhinitis and other allergic diseases found in westernised English-speaking countries.
What is the mechanism of allergic rhinitis?
Allergic rhinitis is a hypersensitivity response to specific allergens in sensitised patients that are mediated by IgE antibodies. Sensitised patients with allergic rhinitis have IgE antibodies for specific allergen(s) bound to receptors on the surface of mast cells. On re-exposure to the specific allergen(s), cross-linking of adjacent IgE molecules occurs, and mast cell degranulation (rupture) takes place, releasing a variety of chemical mediators that may be performed (histamine) or newly synthesized (leukotrienes, prostaglandins).
Histamine causes the cardinal symptoms of allergic rhinitis including sneezing, nasal itching, and runny nose. The nasal congestion is more due to leukotrienes than to histamine. Hence antihistamines are not very good at relieving nasal congestion.
A large number of patients with allergic rhinitis will have an increase in sensitivity to allergens after repeated daily exposure; an effect called "priming". At the start of the pollen season, comparatively large doses of pollens are needed to trigger an allergic response but toward the middle and end of the season, patients become extremely reactive to even small amounts of pollen.
How is allergic rhinitis diagnosed?
The history: It should be ascertained whether the allergic symptoms are seasonal or perennial. The exact month of the year that symptoms start could give a clue as to the specific type of pollen involved.
The tree pollen season starts in late winter and usually ends before the grass pollen season in spring. The weed pollen season overlaps with the grass season, usually starting in late spring and extending through to end of summer.
Patients who are allergic to their pets will often deny obvious symptoms related to contact with their own pets. This is due to some sort of tolerance developed due to continuous exposure to the allergen. If they were to go away for a two week vacation, they might notice immediate symptoms upon their return.
The predominance of nasal symptoms on waking may suggest the diagnosis of house dust mite allergic rhinitis.
Nasal examination: Pale, bluish, swollen mucosa (lining).
Skin prick test should be performed to identify the specific allergen(s) involved, so that the correct avoidance measures can be recommended. The skin prick test is a sensitive, simple and cheap diagnostic technique.
How is allergic rhinitis treated?
Broadly speaking there are three main options in the treatment of allergic rhinitis.
1. Avoiding allergens
Total eradication of the allergen is usually not possible, but measures to reduce the allergen in the local environment should be encouraged. The measures to be used will differ depending on the nature of the allergen.
Pollen particles are part of the reproductive mechanism of plants and are an environmental contaminant, which are difficult or impossible to eliminate. Measures, which can help to reduce the exposure, include:
Keep windows in cars and buildings shut
Wear glasses or sunglasses
Avoid open grassy places, particularly in the evening and at night
Use a car with a pollen filter
Check the pollen count in the media
During the peak season take your holidays by the sea or abroad
House dust mite
House dust mites are found in mattresses, pillows, bedcovers, carpets and soft furnishings throughout the home. Optimal conditions for mite growth is achieved through well-insulated, centrally heated homes!
Mattress/bedding barrier intervention has been shown to reduce mite allergen levels and improve clinical symptoms of both rhinitis and asthma.
The major cat allergen is a salivary protein, which is preened on to the fur where it dries into flakes, which become airborne for many hours and are easily breathed in.
Families with atopic (allergic) members should be advised against furred animals in the home. Psychological factors may render dogmatic statements about removal of a family pet unwise.
Where removal of a pet is not possible, advice can be given to confine the animal outside the house.
Recent studies have suggested that washing the cat (once weekly) when combined with other cleaning measures may effectively reduce airborne cat allergen levels in the home.
2. Drug treatment
Patients need drugs for allergic rhinitis if avoiding the allergen is impossible or fails to control the symptoms.
In recent years, the mainstay of treatment for allergic rhinitis has been the use of topical corticosteroid nasal sprays, and the newer non-sedating antihistamines. These may be highly effective when used either alone or in combination.
Topical sodium cromoglycate represents an alternative anti-inflammatory agent to corticosteroids, particularly in young children.
Topical anticholinergic drugs (e.g. atrovent) and decongestants may have a part to play in defined circumstances.
Corticosteroids and sodium cromoglycate affect the underlying allergic process and should be used as first-line treatment for most patients. Compliance may be a problem with cromoglycates, as they need to be used 3-6 times per day.
Antihistamines and decongestants simply relieve symptoms.
Topical decongestants should not be used for more than 5 days because of rebound congestion.
Immunotherapy is the injection of increasing doses of the identified allergen(s), in order for the body to build up a resistance to it.
Both seasonal and perennial allergic rhinitis may, in general, be effectively managed with a combination of allergen avoidance measures plus topical corticosteroids and oral non-sedating antihistamines. There remains a small group of subjects who, despite regular use of medication, continue to have marked symptoms or unacceptable side-effects from their medication. These patients should be offered immunotherapy.