Disease Information
Allergies > Doctors: Rhinitis Information
Doctors
Epidemiology
Allergic rhinitis is the most common allergic disease, affecting 20–40 million people in the US alone, including 10-30% of adults and up to 40% of children. In the US, the prevalence of seasonal and perennial allergic rhinitis in the general population is about 10% and 10–20% respectively.
Allergic rhinitis is more common in children than adults and is one of the major chronic conditions in children <18 years old. In 80% of cases, it develops before the age of 20 years. Symptoms develop by 2–3 years of age in 20% of cases, and 40% of cases have symptoms by 6 years .
Prevalence is greater in boys than girls, but there is little difference between the sexes in adulthood. Symptoms tend to improve with age, particularly in those who have an early onset of the disease.
The prevalence of allergic diseases varies worldwide. The International Study of Asthma and Allergies in Childhood (ISAAC) found that 12-month prevalences of allergic rhinoconjunctivitis in 13–14 year olds varied between 1.4% and 39.7%: low prevalences were found in Albania, Georgia, Estonia, Lativia, Romania, and Indonesia, and high prevalences were found in Nigeria, Paraguay, Malta, Hong Kong, and Australia.
The prevalence of allergic rhinitis is increasing in both adults and children, particularly in populations with a Western lifestyle: the number of children affected has doubled in the last 20 years. The cause of this increase is uncertain, but possible factors include higher levels of airborne pollution, increased levels of hygiene (the hygiene hypothesis), rising dust mite populations, less ventilation in houses and offices, dietary factors, and the trend towards sedentary lifestyles.
Risk Factors
The prevalence of allergic rhinitis is greatest in higher socioeconomic classes, in non-whites, in polluted areas, in people with a family history of allergy, and in people with positive allergy skin tests.
First-born children, and those born during the pollen season have a higher risk of developing allergic rhinitis. Similarly, children who are introduced early to foods or formula, are exposed to heavy maternal smoking in the first year of life, are exposed to indoor allergens (eg animal dander), and have high serum IgE (>100 IU/mL) levels before the age of 6 years are at increased risk of developing the disease.
The Hygiene Hypothesis
The prevalence of allergic diseases is increasing in adults and children.
The hygiene hypothesis proposes that the increase in the frequency of atopic disease is associated with reduced microbial exposure in early life, as a result of improved sanitation and living conditions that reduces exposure to infections. In the US, serological evidence of acquisition of infections, mainly food-borne and oral-faecal infection, is associated with a lower probability of having allergic rhinitis and asthma. Furthermore, in Europe, atopic disease is reported to be less frequent in children raised in large and poor families, on farms, in communities with a traditional lifestyle, and in children attending daycare centres.
Increased exposure to beneficial microbes early in life may thus reduce the incidence of atopic disease. In a randomised, double-blind, placebo-controlled trial, probiotic bacteria (cultures of bacteria from healthy gut microflora) were administered to pregnant women and their young infants. The frequency of atopic eczema in the probiotic group was half that in the control group.
Classification of Allergic Rhinitis
There are three types of allergic rhinitis:
- seasonal allergic rhinitis
- perennial allergic rhinitis
- perennial allergic rhinitis with seasonal exacerbations
Seasonal Allergic Rhinitis
Approximately 20% of all cases of allergic rhinitis are seasonal allergic rhinitis. This is commonly caused by tree, weed, and grass pollen, and mould spores.
It is an acute disease with symptoms that occur seasonally, when pollen and mould spores are airborne. Peak atmospheric pollen counts occur in June-July for grasses, in May for trees, and July-September for weeds and mould spores. For a worldwide pollen calendar, including information on regional allergens, please see the HON foundation website.
Following pollen exposure, typical symptoms include profuse watery rhinorrhoea, itching, and sneezing. Nasal congestion and allergic symptoms of the eye may also occur.
Hyperresponsiveness to irritants such as tobacco smoke, noxious odours, changes in temperature, and exercise may occur after the pollen season.
Perennial Allergic Rhinitis
Approximately 40% of all cases of allergic rhinitis are perennial allergic rhinitis. This is caused by year-round exposure to dust mites, pollen (in those areas where exposure is all year), cockroaches, indoor moulds, and pet dander.
It is a chronic disease, generally lasting for over 9 months of the year. Typical symptoms include nasal congestion, mucous production, with minimal sneezing, itching, and watery rhinorrhoea.
Perennial Allergic Rhinitis with Seasonal Exacerbations
Approximately 40% of all cases of allergic rhinitis have symptoms of perennial disease with seasonal exacerbations.
Other types of rhinitis include:
- infectious
- non-allergic
- occupational
- hormonal
- drug-induced
- food-related
Pathophysiology
When a person has become sensitised to an allergen, subsequent exposure to that allergen causes an allergic response.
The allergic response is divided into two phases:
- the early-phase responses
- the late-phase responses
Early-Phase Responses
Sneezing, itching, and production of clear rhinorrhoea are the common symptoms of early phase allergic responses; nasal congestion may also occur.
When the nasal mucosa has been sensitised to an allergen, re-exposure leads to binding of the allergen to specific IgE that is coated on mast cells and basophils. The mast cells and basophils degranulate and release preformed inflammatory mediators including histamine, tryptase (mast-cell specific marker), kininogenase (generates bradykinin), heparin, and other enzymes. Mast cells also secrete other de novo inflammatory mediators such as prostaglandins and leukotrienes.
The inflammatory mediators induce a series of inflammatory events. They cause blood vessels to leak, resulting in mucosal oedema and watery rhinorrhoea. They stimulate glands, which secrete mucoglycoconjugates and antimicrobial compounds. They also dilate blood vessels, causing sinusoidal filling, and occlusion and congestion of nasal air passages. Furthermore, they stimulate sensory nerves, resulting in the activation of reflexes such as sneezing and itching.
Late-Phase Responses
The late-phase response is clinically very similar to the early-phase response, but nasal obstruction predominates.
The late-phase response occurs within 4–10 hours after allergen exposure. It involves cellular infiltration of the nasal mucosa by eosinophils, neutrophils, basophils, T lymphocytes, and macrophages. These cells cause the release of inflammatory mediators (eg from mast cells), which in turn reactivate many of the proinflammatory reactions of the early-phase response. In addition, cytokines may circulate to the hypothalamus and result in fatigue, malaise, irritability, and neurocognitive deficits.
The nasal mucosa may become hyperresponsive to inflammatory mediators (eg histamine) several hours after antigen challenge. As a result, patients may develop allergic rhinitis symptoms to non-allergic triggers such as cold air and smoke. This may be because of a change in the responsiveness of sensory nerves that increases the propensity for neurogenic inflammation and allows irritants (and not just allergens) to activate the sensory nerves.
Once induced, the inflammatory process within the nasal mucosa may persist for several weeks after allergen exposure.
Diagnoses of Allergic Rhinitis
Diagnosis of allergic rhinitis should include:
- identification of symptoms
- identification of comorbid disorders
- physical examination
- medical history
- allergen testing
- other diagnostic tests
In certain cases, referral to an allergist-immunologist may be useful.
Non-allergic rhinitis is the most common differential diagnosis of allergic rhinitis.
Differential Diagnosis
There are many causes of rhinitis other than allergic rhinitis. The causes of nonallergic rhinitis are listed below.
- Structural and mechanical factors
- Infectious (eg upper respiratory tract infections)
- Inflammatory and immunological
- Physiological
- Other causes
Structural and Mechanical Causes
- Deviated septum and septal wall anomalies
- Hypertrophic turbinates
- Adenoidal hypertrophy
- Foreign bodies
- Nasal tumours (benign or malignant)
- Choanal atresia
Infectious Causes
- Acute (viral, bacterial)
- Chronic (bacterial, fungal, associated with immune deficiency)
Inflammatory and Immunological Causes
- Wegener's granulomatosis
- Sarcoidosis
- Midline granuloma
- Systemic lupus erythematous
- Sjögren syndrome
- Nasal polyposis
Physiological Causes
- Ciliary dyskinesia syndrome
- Atrophic rhinitis
- Hormonally-induced (hypothroidism, pregnancy, oral contraceptives, menstrual cycle, exercise, atrophic)
- Drug-induced (rhinitis medicamentosa, oral contraceptives, antihypertensive therapy, aspirin, nonsteroidal anti-inflammatory drugs)
- Reflex-induced (gustatory rhinitis, chemical or irritant-induced, posture reflexes, nasal cycle)
- Environmental factors (odours, temperature, barometric pressure, occupational)
Other Causes
- NARES (nonallergic rhinitis with eosinophilia syndrome)
- Perennial nonallergic rhinitis (vasomotor rhinitis)
- Emotional factors
Allergic Rhinitis and Health-Related Quality of Life
It is common for sufferers of allergic rhinitis to be troubled their symptoms, eg repeated nose blowing, fatigue from disturbed sleep patterns, and a reduced ability to concentrate. Children may experience anxiety, inability to integrate with peers, family dysfunction, and learning may be impaired.
Health-related quality of life is therefore reduced by allergic rhinitis and this impairment generally increases in relation to the severity of disease. It is important for physicians to be aware of this impact when considering the most appropriate treatments for the disease. The quality of life of parents whose children have allergic rhinitis may also be reduced.
Questionnaires can be used to quantify the impact of allergic rhinitis on patients' health-related quality of life, for example, the Rhinoconjunctivitis Quality of Life Questionnaire, the Adolescent Rhinoconjunctivitis Quality of Life Questionnaire, and the Paediatric Rhinoconjunctivitis Quality of Life Questionnaire. These assessments are increasingly used in clinical trials to help develop treatments that can improve the symptoms that patients' perceive as important, although they are not generally used in primary care. Therapy may itself exert a negative effect on health-related quality of life, eg side effects such as sedation may affect a person's ability to do daily tasks.
Comorbid Disorders of Allergic Rhinitis
Allergic rhinitis may cause a chronic state of nasal inflammation and obstruction. This is often associated with the following disorders of the lower and upper airways, which may cause significant morbidity:
- Asthma
- Sinusitis
- Otitis media
- Nasal polyps
- Obstructive sleep apnoea
When a patient has comorbid disorders, it is important to consider the overall therapy that the patient receives. For example, if a child is treated for allergic rhinitis, asthma, and eczema by different specialists, it is likely that for many months they may receive inhaled steroids, intranasal steroids, topical cutaneous steroids, and occasional courses of oral steroids. A co-ordinated approach that prevents steroid-loading and its potential side effects is obviously required.
Allergic rhinitis may be a causative factor in the development of the above diseases. Early identification and treatment of allergic rhinitis is likely to be important in preventing or reducing the morbidity caused by its associated disorders.
The Economic Cost of Allergic Rhinitis
The economic cost of allergic rhinitis includes:
- the direct cost of diagnosing and treating the disease
In the US, the direct healthcare costs of treating allergic rhinitis were estimated at $1.2–1.5 billion in 1994.
- indirect costs related to reduced productivity at work (from sick leave and the reduced amount of work done whilst feeling unwell)
In the US, allergic rhinitis accounts for at least 2.5% of visits to doctors, 2 million lost school days per year, 6 million lost work days per year, and 28 million days of reduced work productivity per year. In the US, work productivity losses associated with allergic rhinitis have been estimated at $601 million per year (comprising losses from days taken off sick and reduced work done whilst feeling unwell) . When the sedating effects of antihistamines are also considered, the indirect cost off allergic rhinitis increases to $5.2 billion.
References
Skoner DP. Allergic rhinitis: definition, epidemiology, pathophysiology, detection, and diagnosis. J Allergy Clin Immunol 2001;108:S2-S8.
Dykewicz MS, Fineman S, Skoner DP, et al. Diagnosis and management of rhinitis: complete guidelines of the Joint Task Force on Practice Parameters in Allergy, Asthma and Immunology. Ann Allergy Asthma Immunol 1998;81:478-518.