Description^[1] 

Allergic rhinitis is a common problem. It affects work and school attendance,^[2] and has significant NHS costs.^[3] It is a risk factor for the development of asthma,^[4] and can be the presenting symptom of a severe systemic illness, eg sarcoidosis or Wegener's granulomatosis.

Allergic rhinitis may be categorised into:

• Seasonal allergic rhinitis/hay fever: this occurs at certain times of the year. When due to tree pollen or grass it is known as hay fever. Other allergens include mould spores and weeds.
• Perennial rhinitis (persistent): this occurs throughout the year. Allergens commonly include house dust mites and domestic pets.

Pathogenesis

Allergic rhinitis is a common condition characterised by an immunoglobulin E (IgE)-mediated inflammation of the nasal mucosa following exposure to allergens.^[1]  This gives rise to a release of preformed mediators (of which histamine appears to be the most important) and chemotactic factors from the mast cells in the nasal mucosa. There is a subsequent increase in epithelial permeability and this prompts migration of inflammatory cells to the area:

• Acute-phase response (minutes):
  • Sneezing occurs within minutes of exposure, due to stimulation of afferent nerve endings.
  • Increase in nasal secretion follows shortly afterwards, to peak 15-20 minutes after contact with the allergen.
• Late-phase response (6-12 hours):
  • Characterised by nasal obstruction (although some of the acute symptoms may persist).

Epidemiology

• Allergic rhinitis is a common problem, affecting over 20% of the UK population.^[5]
• Onset is under the age of 30, with a peak incidence in childhood and adolescence.^[6]
• School-aged children and adolescents are more likely to suffer from seasonal allergic rhinitis whereas adults tend to suffer from persistent allergic rhinitis.^[1] 
• True prevalence is unknown on account of the high number of unreported, self-medicating patients. However, it is known to be high in the UK, which had the second highest rate (estimated between 10 and 20%) in Europe of symptoms reported among young teenagers interviewed in an international study.^[7]
• Prevalence appears to be on the increase, which may be due to an earlier onset of spring,^[8] particularly in Europe, due to climate changes. One American study found that 50-70% of all allergic rhinitis patients may also be suffering from non-allergic rhinitis. The authors termed this 'mixed rhinitis'.^[9]

Aetiology

There appear to be both genetic and environmental factors contributing to the development of allergic rhinitis. The most common allergen is the house dust mite, followed by cats and dogs.^[10] There may be associations with other conditions:

• Conjunctivitis - more common in intermittent disease.
• Atopy (including eczematous dermatitis and asthma) - more common in persistent disease.
• Sinusitis and nasal polyps - more common in persistent disease.^[6]

Those most at risk are:^[11]

• Patients with a history of atopy.
• Patients with a family history of rhinitis.
• First-born children.
• Immigrants.

Presentation^[1] 

Seasonal rhinitis tends to occur in the spring or summer. A clue to the allergen can be obtained from the timing of symptoms. Tree pollen tends to cause rhinitis in the spring, whereas grass and weeds cause symptoms in the summer. Occasionally, rhinitis occurring in the late summer/early autumn is seen, due to mould spores.

Symptoms

Listen to the patient's account of symptoms:

• What is the main symptom?
• How long has the condition been present?
• How frequent and severe is it?
• Is it seasonal or perennial?
• Are there trigger factors - allergic or non-allergic?
• Is there exposure to allergens through occupation or hobbies?
• Does the patient have history of asthma, eczema, rhinitis?
• Is it drug-induced or food-induced? Remember that topical sympathomimetics, some antihypertensives, aspirin and non-steroidal anti-inflammatory drugs may cause rhinitis symptoms (see directly below).
• Holiday time remission suggests an environmental cause.

Typical symptoms may include:

• Sneezing.
• Rhinorrhoea and nasal congestion:
  • This may be either anterior or posterior, leading to postnasal drip.
  • Clear - infection unlikely
  • Unilateral - is uncommon - cerebrospinal fluid (CSF) leak should be excluded.
  • Yellow-coloured implies allergy or infection.
  • Green-coloured is usually associated with infection.
  • Blood-tinged unilateral - tumour, foreign body or nose picking.
  • Blood-tinged bilateral - bleeding points, nose picking or granulomatous disorder.
• Itchy nose and/or palate.
• Symptoms tend to be bilateral, and worse on waking.

Examination

• Ear, nose and throat surgeons examine the nose with a head mirror or headlight and a nasal speculum, supplemented by rigid or flexible nasendoscopy.
• In general practice, the nose can be examined with an auriscope fitted with the largest speculum.
• A large, swollen, oedematous inferior or middle turbinate can easily be confused with a polyp; polyps, however, unlike turbinates, are usually pale grey, translucent and mobile and lack any sensation on gentle probing.^[10]
• Look for signs suggestive of chronic nasal congestion - mouth breathing, cough, halitosis.
• Examine eyes for signs of conjunctivitis.
• Rule out other associated conditions.

Complications^[1] 

A survey of adults found that about a third of allergic rhinitis sufferers found that symptoms affected their work, home life and social life.
In children, symptoms affected their schoolwork and caused sleep problems.
Persistent blockage of intranasal passages occasionally results in rhinosinusitis.
In adults, a strong association exists between nasal polyps, asthma and sensitivity to aspirin - Samter's triad.^[10]

Differential diagnosis

• Non-allergic rhinitis.
• Infective rhinitis.
• Nasal polyps.
• Rhinosinusitis.
• Adenoidal hypertrophy.
• Cystic fibrosis.
• Kartagener's syndrome.
• Systemic lupus erythematosus and granulomatous conditions, eg Wegener's granulomatosis and sarcoidosis.
• Consider foreign bodies in the young child.
• Other causes of nasal obstruction.
• Leaking of cerebrospinal fluid will present with watery rhinorrhoea, often unilateral. It is usually associated with trauma (including surgical trauma) or neoplasia, but spontaneous leaking may occur.
• Nasal neoplasms are rare; the diagnosis should be considered in patients with unilateral symptoms of nasal obstruction, pain or bleeding.

Investigations

History and examination should be sufficient to make the diagnosis, but additional allergy testing may be helpful when the causative allergen is not clear.

Skin prick test

Evidence from controlled trials shows the high sensitivity and specificity of skin tests.^[12] One study found that skin prick testing was superior to patient-reported allergies or obtaining a structured allergy history,^[13] although it is not infallible.^[14]

• They are important if avoidance measures are to be considered.
• When skin prick tests are not available or the patient is taking antihistamines or has dermatographism, total and allergen-specific IgE concentrations in the blood may be determined (radioallergosorbent test (RAST)) or enzyme-linked immunosorbent assay (ELISA).^[10]

If this is inconclusive, the list of differentials should be considered.

Objective measures of nasal airway

These are not made in routine clinical practice but can be useful when allergen or aspirin challenges are undertaken and may be helpful when septal surgery or turbinate reduction is being contemplated. They include peak nasal inspiratory flow, acoustic rhinometry and rhinomanometry. 

Computed tomography scan

This is indicated when medical treatment has failed, the diagnosis of chronic rhinosinusitis is suspected and could not be confirmed on history and examination, or neoplasia is suspected.

Management

A stepwise approach according to the severity of symptoms, based on the available randomised trials, has been adopted by 'Allergic Rhinitis and its Impact on Asthma' (ARIA).^[15]

The main lines of treatment are education, allergy avoidance, antihistamines and topical steroids.

The British Society for Allergy and Immunology advises referring the patient to an allergy clinic once all available therapeutic options have been exhausted. Obviously, this is a guideline and the decision as to when to refer should be based on clinical judgement after discussion with the patient/parent/carer.^[5]

General principles

Treatment strategy is guided by the degree of disruption caused by symptoms; the basic principle is to avoid the causative allergen.

Perennial allergic rhinitis is most commonly associated with allergy to house dust mite. A Cochrane systematic review examined whether effective reduction of mite levels was achieved with avoidance measures. Many trials were of poor quality but it was found that the use of acaricides and extensive bedroom-based environmental control programmes may be of some benefit. Isolated use of house dust mite impermeable bedding was unlikely to be effective.^[16]

Medical treatment

• Topical nasal antihistamines:
  • They have superior effects to oral antihistamines for rhinitis symptoms, but do not reduce symptoms at other sites, eg the eyes.^[17]
  • They are fast-acting (less than 15 minutes) so are a useful 'rescue'.
• Oral antihistamines:
  • Regular therapy is more effective than 'as required'.
  • A recent review of randomised controlled trials (RCTs) confirmed the efficacy of oral antihistamines in persistent allergic rhinitis.^[18]
  • Their effect is predominantly on neurally mediated symptoms of itch, sneeze and rhinorrhoea.
• Topical intranasal steroids:
  • Most patients will attain good control on intranasal steroids and a large body of data shows that they are effective for all symptoms of allergic perennial rhinitis, including nasal obstruction, itching, sneezing and watery rhinorrhoea.^[19]
  • Modern intranasal steroids are safe for long-term use in adults when used within the recommended dosage.
  • In children, they should be used at the lowest dose that controls symptoms, particularly when used concurrently with other inhaled or intranasal steroids.^[20] Beclometasone has a worse safety profile than mometasone, budesonide or fluticasone.^[5]
  • Occasionally, intranasal steroids may be associated with dryness, crusting or slight bleeding, which, if recurrent, may necessitate withdrawal of treatment.
  • A Cochrane review concluded that in children it is not worth adding oral antihistamines to intranasal steroids as the risks outweigh the benefits.^[21]
• Others:
  • Sodium cromoglicate is less effective than antihistamines and corticosteroids and needs frequent use (up to five times daily), which may compromise compliance.
  • The anticholinergic intranasal agent ipratropium bromide is effective in controlling watery rhinorrhoea, particularly if this is the dominant symptom. The dose may need to be titrated against symptoms.
  • Oral antileukotrienes have been shown to be effective in allergic rhinitis in RCTs, particularly when combined with oral antihistamines.^[22] They may be beneficial in patients with aspirin sensitivity.
  • Nasal saline washouts have been found to have a beneficial effect in some patients and can reduce the need for intranasal steroids.^[23]

Other treatments such as nasal decongestants and oral steroids should be used only in certain situations:

• Topical nasal decongestants may be useful at the start of treatment to 'open up' the nose and should be used for less than two weeks to avoid the risk of developing 'rhinitis medicamentosa'.
• Oral steroids should be used only as a last resort when other treatments have failed.

Surgical treatment

When drugs fail and a structural abnormality exists, surgery may be indicated:

• Surgical reduction of the inferior turbinates or correction of a deviated nasal septum or nose may be needed to improve the airway or at least to improve access for topical medical treatment.
• Surgery has a role in the management of nasal polyps and sinusitis when these conditions fail to respond to medical treatment,^[24] particularly with the advent of minimally invasive endoscopic sinus surgery.

Immunotherapy^[25] [26]

The preparations available in the UK are vaccines containing house dust mite, animal dander (cat or dog) or extracts of grass or tree pollen. In view of safety concerns, they are only indicated in patients who have failed to respond to anti-allergic drugs. They are recommended only for administration by specialists. Asthma is a relative contra-indication. Other contra-indications include pregnancy, children aged under 5 and patients taking betablockers (adrenaline may be ineffective in the event of an anaphylactic reaction and angiotensin-converting enzyme (ACE) inhibitors (risk of severe anaphylaxis).

A sublingual form of pollen extract is available (Grazax®).^[27][28] This should also only be used if there is no response to anti-allergy treatment. It is licensed for adults and children over the age of 5. One tablet should be taken daily, starting at least four months before the start of the pollen season and continued for up to three years. Absolute contra-indications include malignancy, immune deficiency, inflammatory conditions of the oral cavity and patients with severe or uncontrolled asthma. It should not be initiated in pregnancy but may be continued in patients who become pregnant during treatment, after evaluation including lung function.

Complications^[29]

• Sinusitis
• Nasal polyps
• Chronic otitis media^[30]

Prognosis

This condition often improves over the years - particularly seasonal allergic rhinitis, which may spontaneously resolve in up to 20% of patients.^[1]