Allergic rhinitis

Allergic rhinitis is a common condition secondary to IgE-mediated inflammation of the nasal mucosa.

Allergic rhinitis is a common condition characterised by sneezing, runny nose (i.e. rhinorrhoea), nasal obstruction and itching. It is more colloquially known as ‘Hayfever’. These symptoms are brought about by IgE-mediated inflammation secondary to antigens known as ‘allergens’ that can include grass, tree pollen, or house dust mites among many others.

The diagnosis of allergic rhinitis is clinical and management aims to dampen the immune response to allergens principally with anti-histamines and intranasal glucocorticoids. It may be a very disabling condition and is commonly associated with other ‘allergic’ disorders including asthma, rhinosinusitis, eczema, and allergic conjunctivitis.

Allergic rhinitis is a common condition affecting around 1 in 4 people in the UK.

Allergic rhinitis is common and the prevalence of the condition is increasing. In England, up to 19% of 13-14 year olds are affected by the condition. The peak lifetime prevalence occurs in young adults 15-19 years old. Across other industrialised countries the numbers are similarly high.

The significant increase in rates of allergic rhinitis, and other allergy disorders, is thought to be due to multiple environmental factors. Some of these factors include improved hygiene, eradication of parasitic worms, change in ventilation and heating, and an alteration in diet and lifestyle factors. In addition, there is increasing interest in how these factors influences epigenetic markers. Epigenetics being the way an organism can alter gene expression without changing the underlying sequence.

Allergic rhinitis is due to an IgE-mediated inflammatory responses to one or more allergens.

The term ‘allergy’ or ‘allergic’ or ‘atopy’ essentially refers to the predisposition to mount an IgE-mediated antibody response to otherwise non-harmful environmental antigens (i.e. allergens). We know that some patients have a genetic predisposition to developing this type of reaction.

Allergens

Several environmental allergens may trigger allergic rhinitis. These include:

• House dust mites
• Grass, tree, and weed pollens
• Moulds (e.g. Aspergillus)
• Animal dander (e.g. cat and dog hair)
• Occupational (e.g. chlorine, wood dust)

IgE-mediated reaction

IgE is one of five types of antibody in the body. IgE, like all antibodies, are produced by B cells. IgE is normally involved in defence against parasitic disease, but is also central to the pathophysiology of ‘allergic’ disease.

There are two main phases of an IgE-mediated allergic reaction:

• Sensitisation: an allergen is encountered by T-helper type 2 (Th2) cells that activates B-cells within lymphoid tissue. These B cells then release IgE that binds to mast cells and basophils located throughout the body.
• Re-exposure: if the same allergen is encountered in close proximity to mast cells it can bind IgE antibodies that leads to degranulation with release of chemical mediators (e.g. histamine, tryptase, leukotrienes). This leads to local inflammation, vessel dilatation, loss of vascular integrity and oedema.

In allergic rhinitis, genetically predisposed individuals who are prone to formation of this IgE-mediated inflammation undergo sensitisation. On subsequent re-exposure to the culprit allergen in the nose there is activation of mast cells and basophils. This leads to release of histamine and other chemical mediators that cause the typical symptoms of allergic rhinitis (e.g. sneezing, rhinorrhoea, congestion). The nasal epithelium of patients with allergic rhinitis have significantly more basophils and mast cells than non-allergic patients.

Finally, exposure of the nasal epithelium to allergens can either lead to an immediate or late reaction.

• Immediate: reaction with seconds to minutes of exposure. This usually peaks after 15-30 minutes
• Late: reaction that peaks at 6-12 hours after exposure. Important in development of chronicity of the condition

Allergic rhinitis is characterised by sneezing, rhinorrhoea, nasal congestion, and nasal itching.

Allergic rhinitis can cause a multitude of clinical features, which include:

• Runny nose (i.e. rhinorrhoea)
• Sneezing
• Nasal obstruction
• Nasal itching
• Post-nasal drip: mucous gathers and drips at the back of the throat
• Cough
• Irritable throat
• Fatigue
• Dark shadows under eyes: a feature of ‘chronic congestion’
• Swollen nasal mucosa: often seen as greyish discolourisation
• Horizontal nasal crease (severe cases)

In younger children, instead of blowing their nose there may be features of repeated snorting, sniffing, coughing or throat clearing.

Pattern of symptoms

Patients with allergic rhinitis may have persistent or intermittent symptoms.

• Persistent: symptoms for ≥4 days per week for ≥4 weeks
• Intermittent: symptoms < 4 days per week for < 4 weeks

In line with this, the term ‘seasonal’ is often used to denote intermittent symptoms occurring at a particular time or year, whereas ‘perennial’ describes persistent symptoms all year round.

Severity of symptoms

Symptoms associated with allergic rhinitis may be very debilitating. Symptoms can be broadly divided into mild or moderate-to-severe.

• Mild: normal sleep, no impairment of performance or daily activities, non-troublesome symptoms.
• Moderate-to-severe (≥ 1): disturbed sleep, impaired performance (work/school), impaired activities daily living, troublesome symptoms.

Allergic rhinitis is typically a clinical diagnosis based on characteristic signs and symptoms.

The diagnosis of allergic rhinitis may be made based on typical clinical features of rhinorrhoea, nasal congestion, nasal itchiness, and sneezing. Allergy testing can be done to prove the presence of sensitisation to allergens but is not required for the diagnosis.

Often, the diagnosis is clear by the presence of ‘seasonal’ symptoms. For example, symptoms in the spring and summer months due to tree and grass pollen. Other common examples may be a very specific trigger, for example, animal fur. Patients with persistent or perennial symptoms are most commonly due to indoor allergens such as house dust mites.

Allergy testing

Allergy testing is rarely needed to confirm the presence of sensitisation to specific allergens and most patients can be treated empirically. However, if testing is required there are two main methods:

• Skin prick testing: the patients’ skin is exposed to a specific allergen via a small skin puncture or scratch and the skin is then observed for a cutaneous allergic reaction.
• Allergen-specific IgE antibodies: blood is drawn from the patient to look for IgE-specific antibodies to common allergens. This is more expensive and less sensitive compared to skin-prick testing for inhaled allergens.

NOTE: ~15% of people with a positive skin prick test do not develop symptoms when they are exposure to the allergen. This means a clear clinical history in combination with a positive skin prick test is needed to make the diagnosis.

Associated conditions

Allergic rhinitis is associated with a number of allergic-type conditions and clinical features may co-exist. These include:

• Allergic conjunctivitis (seen in up to 60%): itching, tearing, conjunctival oedema, watery discharge, burning, and photophobia
• Rhinosinusitis: mucopurulent nasal discharge, nasal congestion, and facial pain or pressure
• Asthma (seen in up to 50%): cough, wheeze, and chest tightness
• Atopic eczema: itchy erythematous patches and papules

Patients should be given basic self-management strategies, but if needed, drugs include antihistamines and/or intranasal corticosteroids.

All patients with allergic rhinitis should be given basic self-management advice. This will depend on what types of allergens the patient is sensitised too, but can include:

• Avoid grassy open spaces
• Keep windows shut in cars
• Use synthetic pillows
• Choose wooden floors > carpets
• Regularly clean surfaces
• Keep animals outside the house
• Use latex-free gloves

Pharmacological options

Patients can be advised simple measures such as nasal irrigation with saline that can be bought over the counter.

Patients with intermittent symptoms could be advised to have ‘as-needed’ medications that include:

• Intranasal antihistamines (e.g. azelastine)
• Oral antihistamines: sedating (e.g. chlorphenamine) or non-sedating (loratadine)
• Intranasal sodium cromoglicate

Patients with more persistent, or severe, symptoms can be prescribed ‘stronger’ intranasal preparations:

• Intranasal corticosteroids (e.g. mometasone furoate): depending on the type of allergy, patients may require a prolonged period of treatment, particularly if there is going to be ongoing exposure

Advanced therapy

Some patients may have persistent symptoms that fail to respond to conventional therapy. A variety of options are available depending on the predominant symptoms and may be combined with first line therapies. These include:

• Intranasal decongestants (e.g. xylometazoline)
• Intranasal anticholinergic (e.g. ipratropium bromide)
• Leukotriene receptor antagonist (e.g. montelukast): mainly if co-existent asthma
• Oral corticosteroids (short course): should be reserved for severe, uncontrolled symptoms that significantly impacting quality of life

Referral

If the diagnosis if unclear, there is a suspected precipitating cause (e.g. deviated nasal septum), or troubling symptoms despite conventional therapy then patients may require referral to specialist ENT or allergy services. Allergy services, in particular, may be able to offer allergen immunotherapy or biologic therapy (e.g. omalizumab – a monoclonal antibody against IgE).

Pollen food allergy syndrome mostly occurs in patients with allergic rhinitis.

Pollen food allergy syndrome, also known as oral allergy syndrome, is a type of food allergy when patients react to allergens contained within raw fruit and vegetables. It is commonly seen in patients with allergic rhinitis due to the cross-reactivity of certain aeroallergens (e.g. birch pollen) with those of raw fruit and vegetables.

Clinical features typically affect the lips, mouth, tongue and throat. They include swelling, itching, or tingling when they come in contact with the allergen. Severe allergic reactions (e.g. anaphylaxis) can occur, but are thankfully rare.

Common culprit foods include:

• Apples
• Apricots
• Pears
• Cherries
• Kiwi
• Mango
• Plums
• Peaches
• Carrots
• Celery