What is Allergic Rhinitis?
Rhinitis refers to inflammation of the nasal passages which results in symptoms such as sneezing, nasal congestion and blockage. Rhinitis which is caused by an allergic trigger is known as Allergic Rhinitis. This accounts for about 75% of rhinitis cases while the remaining 25% are caused by non-allergic rhinitis.
Allergic Rhinitis may be classified as either seasonal or perennial. Perennial Allergic Rhinitis occurs throughout the year and is most often caused by house dust mite and animal dander. Seasonal Allergic Rhinitis is known as Hay Fever and is caused by an allergy to pollen.
Pathophysiology of Allergic Rhinitis
Allergic Rhinitis occurs when the immune system misidentifies a specific airborne allergen as a threat and directs an inflammatory response against it. The immune system generates specific memory against the specific allergen so that any future exposure triggers a more aggressive Immunoglobulin E (IgE) mediated immune response characterised by the release of histamine, leukotrienes, prostaglandins and other chemical mediators.
When the nasal passages are examined endoscopically in those who suffer from allergic rhinitis the findings often include bulky oedematous nasal turbinates with visibly increased mucus production. In chronic allergic rhinitis, the nasal mucosa can lose its smooth appearance and become pale and pitted. In some cases nasal polyps may develop and can contribute to the severity of the symptoms.
Causes of Allergic Rhinitis
The most common causes of Allergic Rhinitis are airborne allergens such as:
- House dust mite
- Animal dander (cat, dog, horse etc)
Genetic Predisposition to Allergic Rhinitis
Allergic Rhinitis appears to be the consequence of environmental exposures in those with a genetic vulnerability. Indeed, genetic predisposition or atopy accounts for at least 50% of AR cases and genetic studies have demonstrated that multiple susceptible genetic loci can contribute to Allergic Rhinitis alone.
Prevalence of Allergic Rhinitis
Allergic Rhinitis is a common condition with a global impact. It is estimated that allergic rhinitis affects at least 400 million people worldwide and the prevalence in Europe is between 17 and 29%. In Ireland, we are likely to have a prevalence of about 26% in line with UK studies.
The Economic Impact of Allergic Rhinitis
The economic impact of Allergic Rhinitis is striking. The European Union recently estimated that the indirect cost of undertreated allergic rhinitis on work productivity is €30 - €50 billion per year.
What is Non-Allergic Rhinitis?
Rhinitis that occurs without a known allergic trigger is called non-allergic rhinitis. This accounts for about 25% of rhinitis cases. Non-allergic rhinitis can be caused by structural nasal problems such septal deviation and also through exposure to environmental pollution, chlorinated pools and even fragrances. Hormonal changes such as those found during puberty, pregnancy and menopause can also act as a trigger.
Seasonal Allergic Rhinitis - Hay Fever
Hay Fever affects people who are allergic to Grass, Tree or Plant Pollen. In addition to nasal and sinus symptoms, hay fever can also affect the eyes, lungs and skin. Most sufferers are allergic to grass pollen alone but 25% of those with grass pollen allergy also suffer from tree pollen allergy. It is also relatively common to have an allergy to tree or plant pollen without having an allergy to grass pollen.
When is Hay Fever Season?
The Hay Fever season in Ireland occurs mainly in spring and summer but it can last until late autumn. It begins with the release of Tree Pollen in early March until May. This is followed by the Grass Pollen season which occurs from May until September. For those with the extra burden of mould spore allergy the hay fever season can drag on through the autumn months.
The Educational Impact of Hay Fever
In addition to missed work days in adults, allergic rhinitis can have a worrying impact on a child’s education. Missed or unproductive days at school are common. This can become particularly significant as hay fever season coincides with exam time. A UK study of teenagers found that there was a reduction in exam performance for those with hay fever compared with other times of the year. This is most relevant for Leaving Certificate students and those in University.
What are the Symptoms of Hay Fever?
- A runny nose, sneezing and nasal congestion.
- Sinus pressure and pain.
- Itchy red eyes +/- puffiness around the eyes.
- Cough or wheezing.
- Ears popping +/- hearing impairment.
- Reduced sense of taste and smell.
- Itchiness of the roof of the mouth.
- Feeling of fatigue or lethargy.
Hay Fever Symptoms explained
Blocked nose: This is caused by swelling of the nasal lining and turbinates, the soft ‘shelves’ inside the nose.
Sneezing: As the nasal lining swells it becomes irritable and peppered with tiny blister-like swellings.
Runny nose: The swollen and irritable nasal lining produces clear mucus.
Sinus pain: When the passages from the nose to the sinuses become blocked, there is an increase in pressure within the sinuses which manifests as discomfort of the forehead (frontal sinuses) and cheek bones (maxillary sinuses).
Reduced sense of smell and taste: In more severe cases, the swelling of the turbinates in the upper parts of the nose compress the olfactory nerve endings located there. The sense of smell is affected first. By the time you are aware of reduced smell your sense of taste has probably already diminished. The appreciation of spice fades initially and as foods gradually start to taste bland people often begin to add more salt, pepper or spices.
Itchiness of the roof of the mouth: The roof of the mouth lies adjacent and below the base of the maxillary sinuses and may become irritated by pollen entering the airways.
Reduced hearing and ear popping: Further swelling of the nasopharynx causes dysfunction of the eustachian tube which serves the important function of equalising the pressure in the middle ears.
Cough, wheeze or shortness of breath: Inflammation of the nose and sinuses increases the reactivity and irritability of the lower respiratory tract. This can worsen existing asthma or trigger asthmatic symptoms in non-asthmatics.
Itchy red eyes: As pollen irritates the eyes the skin underneath the lower eye lids fills with fluid making them appear puffy. The inner surface of the eye lids may distort with the tell tale ‘cobble-stone’ appearance of allergic conjunctivitis.
Fatigue: Even 50% of these symptoms can leave hay fever sufferers feeling exhausted and drained.
How is Hay Fever diagnosed?
The diagnosis of Hay Fever is usually based on the clinical symptoms and a medical examination. It is important to ensure that your nose, eye and chest symptoms are indeed caused by pollen allergy and not by another medical condition. In Allergy Ireland, our doctors use a combination of history taking, nasoendoscopic examination and skin prick allergy testing to ensure that we arrive at the correct diagnosis and can therefore recommend the most appropriate and effective treatments.
Skin Prick Allergy Testing
Skin prick testing is the gold standard in allergy testing. It is used to confirm which type of pollen is causing the Hay Fever symptoms while also excluding other common allergies such as house dust mite, mould spore or animal dander.
Nasal Endoscopic Examination
This is a painless procedure used to examine the tissues inside the nose. It is carried out by our doctors during your consultation in order to ensure there are no structural issues or polyps present inside the nose.
Hay Fever self-help tips
- Keep windows closed during peak pollen hours.
- especially your bedroom window.
- including while driving!
- Wear wrap-around sunglasses to help block pollen from entering the eyes.
- Wear a face mask if you plan to cut the grass.... or ask a friend!
- Place Vaseline inside each nostril to prevent pollen from entering the nose.
- Shower and change your clothes after walking in the park.
- Wash bedsheets regularly and vacuum the floors.
- Spend leisure time or holidays at the sea as the sea breeze disperses pollen.
- Check for the next day’s pollen count and plan your schedule accordingly.
- Park and grasslands walks during pollen season.
- Being outdoors during peak pollen hours (late morning and late afternoon).
- Smoking as this aggravates allergic symptoms and may even contribute to the development of nasal polyps.
- Drying clothes and bedsheets outside as pollen will settle all over your clothes.
Hay Fever Treatment Options
For suffers of more significant Hay Fever symptoms there are a wide variety of very effective pharmacological treatment options available. These should be used in conjunction with the avoidance measures detailed above as limiting your exposure to pollen is always beneficial for sufferers.
Oral Medication for Hay Fever
In terms of over the counter medications, non sedating oral anti-histamines such as cetirizine (Cetrine), loratadine (Clarityn) and fexofenadine (Telfast) can be useful for patients with mild to moderate symptoms. These can be used on a daily basis during the peak hayfever season or just as required. If anti-histamines result in drowsiness then consider dividing the dose between morning and night or try another brand. Trying different anti-histamines can be useful as many people can find certain anti-histamines either more effective or less sedating than others.
Oral decongestants such as pseudoephedrine (Sudafed) can be used temporarily as a rescue medication.
In cases where asthma or lower airway irritability exists your doctor may prescribe a leukotriene receptor antagonist tablet (montelukast) or steroid inhalers and salbutamol bronchodilators (Ventolin) if this is appropriate.
Nasal Sprays for Hay Fever
Steroid nasal sprays can be considered when nasal symptoms remain very problematic despite the use of anti-histamines tablets. Some brands are available over the counter while others are prescription only. These sprays are considered very safe for seasonal use but need to be taken every day during the Hay Fever season in order to be effective. They should ideally be started several weeks before the start of the Hay Fever season.
Nasal decongestants such as xylometazoline (Otrivine) can be used as a rescue medication but for no longer than 5 days to avoid rebound symptoms.
Saline irrigation is an effective way to directly cleanse the nasal cavity with the resultant reduction of mucus, inflammatory mediators and bacterial burden. It has also been shown to improve mucociliary function.
Eye Drops for Hay Fever
For troubling hay fever eye symptoms (allergic conjunctivitis), cromoglicate eye drops such Opticrom are an excellent over the counter option. These work by blocking the 'mast cells' from releasing histamine in the eyes. Alternatively, anti-histamine eye drops such as olopatadine (Opatanol) may be prescribed by your doctor.
Advanced Hay Fever Treatment Options
Allergen Desensitisation Immunotherapy
Immunotherapy is where you take exactly what you are allergic to but in a modified form. A tablet is taken every day for approximately 3-5 years resulting in desensitisation of the immune system to the allergen. This is particularly effective in people under the age of 30 and typically results in permanent relief. At Allergy Ireland, our doctors use sublingual immunotherapy against Grass Pollen, Tree Pollen and House Dust Mite.
Rhinolight Endonasal Phototherapy
Rhinolight provides a highly effective drug free treatment option for nose and sinus allergy sufferers. It is effective in treating the vast majority of cases of nasal Hay Fever symptoms but it does not have any impact on eye symptoms. Rhinolight is used for short, sharp treatments with the benefits lasting for several years.
Hay Fever Treatment during Pregnancy
It is recommended to cease all medications during pregnancy unless instructed otherwise by your doctor. While none of the medications described above should be used during the first trimester of pregnancy, certain steroid nasal sprays and specific anti-histamines may be used during the second and third trimesters under specialist medical supervision. This should only be done when the benefits outweigh the risks. Rhinolight can be used during pregnancy and is highly effective at treating nasal Hay Fever symptoms. Allergen desensitisation immunotherapy is not started during pregnancy but is safe to be continued during pregnancy.
Does Hay Fever impact on Asthma?
Asthma sufferers with sensitivity to pollen may notice that their asthmatic symptoms can substantially worsen during hayfever season. If the pollen levels are sufficiently high an asthma attack can be triggered in susceptible individuals.
In individuals with Hay Fever, pollen precipitates an allergic response in all of the mucosal surfaces that it comes into contact with. It is therefore not surprising that pollen which enters the sensitive and reactive airways of asthmatics will irritate and also precipitate an allergic response in the lungs just as it does in the nose and eyes.
In addition to pollen directly interacting with the lower airways of the lungs, there is strong clinical evidence that poorly controlled allergic rhinitis itself worsens asthmatic symptoms. This makes it particularly important to manage hayfever and rhinitis symptoms in those who have asthma. This 'united airways' approach is now favoured and results in better clinical outcomes for both conditions.
- Hay fever may cause nose symptoms only.
- Hay fever often involves the sinuses as well as the nose.
- Hay fever may provoke chest symptoms.
- Hay fever may go hand-in-hand with asthma.
- Hay fever in asthmatic children is associated with more asthma-related hospital admissions.
Why does the Pollen Count vary?
The pollen count is a measure of the amount of pollen in the air over a 24 hour period. Pollen begins to be released early in the morning and is carried by warm air currents high into the air by midday. As the air cools in the late evening the pollen descends again. Cities and concrete urban areas stay warmer for longer and in these areas pollen may even descend during the night. Atmospheric pollution from car fumes and industry can combine with pollen to trigger a more aggressive allergic response. This is sometimes referred to as super pollen by the media.
Do local weather conditions affect Pollen Counts?
Local weather conditions have a significant bearing on the production, dispersal and quantity of pollen grains in the air. Higher levels of pollen occur on warm, dry and sunny days. Low pollen levels occur on wet, damp and cold days. Rain washes the pollen from the air while on shore winds help disperse and remove pollen.
Do different countries have different Hay Fever seasons?
Your own pollen season will vary depending on which pollens you are allergic to and where you live. Certain grass and tree pollens predominate in different countries and the peak release of pollen may occur during different months. Pollen from timothy grass, perennial rye and ragweed circulate throughout Europe in addition to Tree Pollens such as birch which is a common culprit. Some pollens are more common in city environments, forests or mountainous areas. It is worth noting that pollen levels are lower by the sea and that the Grass Pollen season starts about 2 weeks later in mountainous areas.
UK and Ireland
- March - May: Tree Pollen season.
- May - September: Grass Pollen season.
Northern, Central and Eastern Europe
- May - July: Grass Pollen season.
- December – March: Tree Pollen (Birch, Cypress, Juniper, Hazel, Mimosa).
- March – May: Tree Pollens such as American Sycamore.
- April – July: Grass Pollen, Nettle and Olive Tree pollen.
- August – October: second flowering of Nettle and Mugwort Weed.
Why is the prevalence of Hay Fever rising?
The cause for the rising prevalence is unclear but risk factors may include overuse of antibiotics, exposure to air pollution, maternal/passive smoking and climatic factors among other theories.
The Hygiene Hypothesis
Certainly, environmental exposures are key to understanding the rising prevalence of allergies. The ‘hygiene hypothesis’ was proposed as an explanation whereby the more sterile Western lifestyle was reducing infections and resulting in less type 1 immune responses. More recently, there is a better insight into the development of allergen tolerance with the microbiome during early life being an essential component. Antibiotic use will disrupt this amongst other environmental factors. Exposure to irritants such as cigarette smoke and air pollution particularly diesel exhaust fumes have been shown to contribute to and exacerbate Allergic Rhinitis.
Global Warming Prolongues the Hay Fever Season
In addition, global warming is seen to be playing a role in Ireland with milder weather resulting in prolongation of pollen and spore seasons. This is confounded by the introduction of new pollens such as ragweed which would usually be a common allergen in North America and Continental Europe.
Further Information for Health Professionals
Epidemiology of Allergic Rhinitis
It is estimated that Allergic Rhinitis affects at least 400 million people worldwide and the prevalence within Europe is between 17 and 29%. The UK has a prevalence of 26% and Ireland is likely to be similar to this.
Allergic Rhinitis will often begin early in life but prevalence increases with age. The International Study of Asthma and Allergies in Childhood (ISAAC, 2006) phase III study demonstrated this showing a 5% prevalence in those aged 3 years, an 8.5% prevalence in those aged 6-7 years and a 14.6% prevalence in those aged 13-14 years.
What is most concerning is that the prevalence of Allergic Rhinitis is increasing globally. This was corroborated by this ISAAC study which found an increase in prevalence of AR from 13% to 19% over an 8 year period in a cohort of 13-14 year olds. A smaller study in Cork demonstrated an increase in prevalence from 7.6% to 10.6% over a 5 year period in a cohort of 6-9 year olds.
Detailed Pathophysiology of Allergic Rhinitis
There are two phases which are paramount to the development of an allergy.
Phase one occurs when an atopic individual is first exposed to the allergen. The allergen is taken up by antigen presenting cells particularly dendritic cells (DC) and is processed into peptide fragments. The DC will move through the lymphatics towards the lymph node where it will present this peptide fragment to a naïve T cell. The naïve T cell becomes activated to express cytokines particularly IL-4 which drives the differentiation of these cells to Th2 helper cells.
An environment rich in cytokines IL-4 and IL-13 is created and is responsible for inducing IgE production from B cells. Additionally, IL-5 is responsible for eosinophil recruitment and activation. The cytokine profile is vital as it determines a Th2 immune response.
In the meantime, T cell dependent activation of B cells stimulates further cytokine production particularly IL-4 and promotes irreversible immunoglobulin class switching to allergen specific IgE antibodies.
Allergen specific IgE will attach to mast cells and basophils. This is referred to as primary sensitisation. In addition, memory B cells are generated and a small number of memory T cells remain.
Phase two occurs on subsequent exposure to this allergen. The allergen binds to the sensitised mast cells triggering degranulation of the mast cell releasing pre-stored and newly synthesised inflammatory mediators such as histamine, leukotrienes and prostaglandins. These contribute to vascular permeability, eosinophil infiltration and increased mucus production.
Furthermore, with repetitive allergen exposure nasal priming occurs. This appears to cause an accumulation of effector cells in the nasal mucosa and results in a hyper-responsiveness to the allergen and prolongation of symptoms. In addition, there appears to be a neural component to this hyper-responsiveness. Changes to the sensory nerves of the nose have been demonstrated in those with Allergic Rhinitis. In addition, innate immune responses can be initiated in the nasal epithelium by allergens directly compromising the epithelium and resulting in the release of alarmins such as IL-33 further activating the inflammatory response.
Adapted from Bousquet et al. Nature Reviews Disease Primers, 2020
Allergic Rhinitis Treatment Guidelines for Health Professionals
Allergen avoidance should be discussed. Nevertheless avoidance alone is generally not sufficient to manage symptoms. In cases where the allergen trigger is animal dander avoidance is effective if the animal is removed from the home.
Smoking cessation should be advised always. Smoking can be associated with chronic nasal symptoms and may even be associated with the development of polyposis. Passive smoking or ‘vaping’ appear to carry similar risk.
Saline irrigation of the nasal cavity reduces accumulated mucus, inflammatory mediators and bacterial burden. It has also been shown to improve mucociliary function.
In patients with mild intermittent symptoms an antihistamine is often effective. Second generation antihistamines are recommended as they carry less cholinergic and sedating side effects. Oral or nasal decongestants can be used as a rescue medication but for no longer than 5 days to avoid rebound symptoms.
The ARIA guidelines recommend intranasal corticosteroids as the first line treatment for moderate-severe intermittent or persistent Allergic Rhinitis. A low bioavailability is recommended and so newer generation intranasal corticosteroids are preferred.
If the nasal cavity is very obstructed a nasal spray may not be effective until the oedema has been reduced using intranasal corticosteroid drops. Should this not be effective a combination intranasal treatment is now available combining corticosteroid and antihistamine.
Eye symptoms can be managed conservatively with cold compresses and tear supplements. However, if these symptoms persist, it is advisable to consider oral and topical antihistamines, topical mast cell stabilizers (sodium cromoglicate) or decongestants. Topical corticosteroids should ideally be prescribed under the care of an Ophthalmologist.
If there is evidence of lower airway irritability or asthma, a leukotriene receptor antagonist can be trialled. In severe cases short courses of oral corticosteroids are occasionally required.
Newer Treatment Options: Immunotherapy
Immunotherapy has been shown to significantly reduce symptoms and medication requirements and is recommended by the ARIA guideline. Additionally, the GINA (Global Initiative for Asthma) guidelines 2022 recommend immunotherapy be considered for asthmatics sensitised to dust mite. Immunotherapy involves exposing a patient to minute quantities of the allergen trigger allowing the immune system to build up a tolerance. It is essentially like a vaccination. It can be given as a subcutaneous injection or as a sublingual tablet. Sublingual therapy is used predominantly in Ireland and is currently available for grass pollen, dust mite and tree pollen. Compliance is crucial and regular follow up advised. It is usually a three year process whereby the patient takes it daily. It is highly effective and well tolerated.
Newer Treatment Options: Endonasal Phototherapy
Phototherapy is well established for skin conditions and is now being used within the nasal cavity to manage Allergic Rhinitis. It uses UV-A (25%), UV-B (< 5%) and visible light (70%) to induce a local immunosuppressive effect by inhibiting allergen induced histamine release from mast cells and inducing apoptosis of T lymphocytes and Eosinophils. It essentially desensitises the nasal cavity thus reducing symptoms. It is particularly useful when pharmacological treatment is insufficient or contraindicated.
Does Allergic Rhinitis co-exist with other atopic conditions?
Multimorbid Allergic Rhinitis is whereby Allergic Rhinitis co-exists with Asthma or Atopic Dermatitis. Interestingly a differing variety of genetically susceptible loci are attributable to multimorbid Allergic Rhinitis for example IL-5 and IL-33 for those with Allergic Rhinitis and Asthma.
Allergic Rhinitis is a risk factor for asthma. In fact, 90% of asthmatics have Allergic Rhinitis and 30-40% of those with Allergic Rhinitis have Asthma. A ‘united airways’ disease approach to management is the more favoured approach in recent years. Moreover, the treatment of nasal inflammation in asthmatics has been shown to improve outcomes. This highlights the importance of assessing for both asthma and rhinitis in these patients.
Allergic Rhinitis can also be associated with comorbid dermatological conditions such as atopic dermatitis and urticaria upon exposure to an allergen. Interestingly, the treatment of Allergic Rhinitis often results in improvements in these dermatological conditions.