Allergic rhinitis belongs to a group of clinical conditions known as “allergies”, in which the immune system overreacts to substances that are usually harmless. Other common allergies are allergic asthma, atopic dermatitis, food allergies and anaphylaxis.
What is allergic rhinitis? It is an inflammatory condition of the upper airways, characterised by sneezing, a runny nose, an itchy nose and nasal congestion. Depending on their intensity, these symptoms can significantly affect quality of life.
Symptoms are triggered by exposure to allergens (substances that can cause an allergy) in the air we breathe. In Portugal, according to SNS 24, most cases are due to allergy to dust mites or pollen. The most common allergens include:
- pollen;
- house dust mites;
- animal hair and dander;
- moulds and fungi.
Other airborne factors, such as tobacco smoke, urban and industrial pollution, some microorganisms and the chemicals in household cleaning products, furniture and home finishing materials, can irritate the nasal lining and make symptoms worse.
There is also much talk about the link between diet, the gut and allergies. The ways in which gut flora may influence immunity are still being studied, but so far a systematic review by the US Department of Agriculture has not found enough evidence to link diet diversity or dietary patterns in the first two years of life with the risk of allergic rhinitis.
In this article, we explain what causes allergic rhinitis, how to recognise the symptoms, how it is diagnosed and which prevention and treatment measures you can adopt to live better with this condition.
Allergic rhinitis: environment and epidemiology
Rhinitis is one of the most common chronic diseases worldwide, according to the Portuguese Society of Allergology and Clinical Immunology (SPAIC). In Europe, the prevalence of pollen allergies has increased over the past decades.
The prevalence of allergic rhinitis varies with geographical location. Environmental factors that influence exposure to allergens include:
- the region where you live and the type of vegetation, which determine the pollen in the air;
- the climate, which influences the length of the pollen season;
- warm, damp and poorly ventilated environments, which encourage the build-up of dust mites and mould.
Why is allergic rhinitis on the rise?
The causes of this increase are not yet fully understood. According to the European Climate and Health Observatory, the rise in pollen allergies in Europe cannot be explained solely by changes in the genetics or health of the population. The factors pointed out include:
- changes in lifestyle and dietary habits;
- changes in hygiene and greater use of antibiotics;
- air pollution and climate change, which lengthen the pollen season and increase the amount of pollen in the air.
The same source notes that combined exposure to air pollutants and allergens can have a synergistic effect on asthma and allergies.
Indoor air quality matters too. Studies by the US Environmental Protection Agency (EPA) found levels of about a dozen common organic pollutants to be 2 to 5 times higher inside homes than outside. What is more, we spend around 90% of our time indoors.
That is why reducing sources of pollution at home and ventilating rooms are useful measures for people with allergic rhinitis, as irritants such as tobacco smoke, perfume or paint fumes can trigger or worsen nasal symptoms.
Pollution may also make pollen more allergenic: long-term high levels of nitrogen dioxide in urban environments are associated with increased pollen allergenicity.
How many people have allergic rhinitis in Portugal and Spain?
In Portugal, the National Asthma Prevalence Survey (INPA), carried out in 2010 with more than 6,000 participants, estimated that 22% of the population has symptoms of rhinitis, according to SPAIC. In adults aged 25 to 64, the ARPA study estimated a prevalence of 26% and, in people aged 65 and over, 30%.
In children aged 3 to 5, the ARPA-Kids study found a rhinitis prevalence of 43%, but 74% of these children had no previous medical diagnosis. This is a public health problem that is often underdiagnosed and undertreated.
In Spain, the Spanish Society of Allergology and Clinical Immunology (SEAIC) estimates that more than 20% of the population has allergic rhinitis.
As in other countries, the prevalence of allergic rhinitis varies with the region and environmental exposure factors, and worldwide estimates range from 10% to 40%.
Causes of allergic rhinitis: how does the allergic reaction develop?
The role of the immune system is to protect us from potential threats. In allergic rhinitis, the defence mechanisms are hyperreactive, out of proportion to the real danger posed by the agent.
The process is triggered by exposure to allergens such as pollen, dust mites, dust, animal hair or fungi. According to a review published in the Revista Portuguesa de Imunoalergologia, the allergic response has two phases:
- Early phase: begins minutes after exposure to the allergen, corresponds to the immune system recognising the offending agent and lasts around 2 to 3 hours.
- Late phase: starts around 4 to 8 hours after exposure to a relevant allergen. It is a predominantly inflammatory phase, characterised by heavy mucus production and nasal congestion.
The changes in the late phase are thought to contribute to bronchial hyperreactivity.
Pollen, dust mites, mould and animal hair act mainly as triggers of the allergic response. In someone who is already sensitised, these allergens are recognised by specific IgE antibodies on immune cells in the lining of the nose, which acts as a trigger that “sets off” the reaction.
This is what happens, for example, with dust mites that build up in mattresses and bedding.
Intermittent or persistent allergic rhinitis
According to the classification of the international ARIA group (Allergic Rhinitis and its Impact on Asthma), allergic rhinitis can be classified by duration (intermittent or persistent) and by severity of symptoms (mild or moderate to severe).
Intermittent rhinitis causes symptoms on fewer than 4 days a week or for less than 4 weeks. It is often linked to pollen, in what is known as seasonal rhinitis or “hay fever”. In Portugal, according to SNS 24, pollen from trees, grasses and shrubs is mainly associated with spring and summer.
Persistent rhinitis causes symptoms on 4 or more days a week and for 4 or more weeks. It may be linked to allergens present all year round, such as house dust mites and animal dander, and can be influenced by the indoor environment, at home or at work. Allergens and irritants found indoors:
- dust mites in mattresses, upholstered furniture, rugs and curtains, which thrive in warm, damp and dark environments;
- mould and fungi, encouraged by excessive humidity and poor ventilation;
- enclosed spaces that are difficult to ventilate;
- irritants such as tobacco smoke, perfume, paint fumes and other chemicals, which can irritate the nose and make symptoms worse.
Mild or moderate to severe allergic rhinitis
Rhinitis is considered mild when it:
- does not interfere with sleep;
- does not interfere with daily, work, school, sports or leisure activities;
- does not cause troublesome symptoms.
It is considered moderate to severe when it interferes with at least one of these situations.
Other types of rhinitis: vasomotor and infectious
Rhinitis means inflammation of the nasal lining and, besides allergy, it has other causes. In non-allergic rhinitis, including so-called vasomotor rhinitis, symptoms can be triggered, according to the NHS, by changes in temperature or humidity, by smoke, perfume or paint fumes, by alcohol or by spicy food.
Infectious rhinitis is caused by infectious agents, such as viruses or bacteria, as happens with colds and flu.
Symptoms of allergic rhinitis
The main symptoms of allergic rhinitis are:
- sneezing, often in bouts;
- nasal pruritus (itchy nose);
- watery rhinorrhoea (runny nose);
- nasal congestion (blocked nose).
At the same time, the following may appear:
- eye symptoms, such as itching, red eyes and watering, which may indicate associated allergic conjunctivitis;
- postnasal drip (discharge running from the nose down the throat);
- tiredness;
- throat irritation with a dry cough, which can become chronic.
Conditions associated with allergic rhinitis
Allergic rhinitis may favour or be associated with bronchial asthma. If, in addition to nasal symptoms, you experience wheezing, chest tightness or shortness of breath, talk to your doctor and find out more in our article on allergic asthma.
Rhinosinusitis, or sinusitis, is inflammation or infection of the lining of the paranasal sinuses, internal cavities in the bones of the face and skull that connect with the nasal passages. It is one of the conditions associated with allergic rhinitis, according to the review in the Revista Portuguesa de Imunoalergologia.
According to SNS 24, untreated rhinitis can also contribute to other health problems, such as otitis (ear inflammation), sinusitis and tonsillitis.
Allergic rhinitis and asthma share a common inflammatory process that affects both the upper airways (nose) and the lower airways (bronchi), which is why the concept of “united airways” is used.
In addition to the conditions already mentioned, other conditions may occur alongside allergic rhinitis, as described in the ARIA guidelines, such as:
- nasal polyposis;
- enlarged adenoids;
- Eustachian tube dysfunction (ears);
- sleep apnoea;
- laryngitis;
- gastro-oesophageal reflux.
How is allergic rhinitis diagnosed?
It is important to make an accurate diagnosis of allergic rhinitis, ruling out other conditions, such as:
- the common cold;
- infectious rhinitis;
- vasomotor rhinitis;
- rhinitis medicamentosa (due to overuse of nasal decongestants);
- chronic sinusitis;
- nasal polyposis;
- deviated nasal septum.
The diagnosis of allergic rhinitis is based on the medical history, examination of the nasal passages and further tests, namely skin prick tests and/or blood tests measuring specific IgE. Skin prick tests involve applying tiny amounts of allergens to the skin and help identify the allergens involved.
There are also other diagnostic methods, either additional or still under investigation, reserved for specific situations.
Allergic rhinitis, sinusitis or a cold: what are the differences?
Main differences between allergic rhinitis, sinusitis and a cold:
| Characteristics | Allergic Rhinitis | Sinusitis | Cold |
| Cause | Allergy | Inflammation or infection | Viral infection |
| Nasal discharge | Clear and watery | Thick, yellow/greenish | Clear at first; then yellow |
| Sneezing | Frequent | Little or none | Occasional |
| Itchy nose, eyes and ears | Yes | No | No |
| Pain in the facial bones | No | Yes (around the cheeks, eyes or forehead) | May occur, but mild |
| Fever | No | May occur | May occur |
| Duration | As long as there is contact with the allergen | Up to about 4 weeks (acute); more than 3 months (chronic) | 1 to 2 weeks |
| Other common symptoms | Nasal congestion; watery eyes | Headache; loss of sense of smell | Sore throat; mild tiredness |
When should you see a doctor?
Seek medical advice if:
- symptoms last a long time or keep coming back;
- symptoms interfere with sleep, work or school;
- over-the-counter medicines do not bring enough relief or you feel the need to use nasal decongestants for many days in a row;
- wheezing, shortness of breath or chest tightness appear;
- you have severe facial pain, fever or thick, greenish discharge, which may indicate sinusitis.
How can you prevent allergic rhinitis?
Reducing contact with the allergens involved can help control the symptoms of allergic rhinitis, although, according to the review in the Revista Portuguesa de Imunoalergologia, scientific evidence for these measures is still limited and complete avoidance is difficult for allergens that are present all year round, such as dust mites.
These measures complement treatment and should be chosen according to the established medical diagnosis, in particular the allergens identified.
We present two groups of measures: dietary and digestive measures, for which evidence in allergic rhinitis is still limited, and respiratory measures, which aim to reduce contact with allergens.
Dietary and digestive measures: diet and gut health
A varied diet with fresh, minimally processed foods is part of a healthy lifestyle. However, so far there is not enough evidence that any specific dietary pattern in the first years of life prevents allergic rhinitis.
As for probiotics (formulations of specific microorganisms that act on the gut flora, or microbiome), the mechanisms by which they may reduce inflammation and intestinal permeability and change the gut flora have been studied mainly in the laboratory and in animal models.
In allergic rhinitis, a 2022 review concluded that there is still substantial uncertainty about the effectiveness of probiotics for prevention and treatment; at present, they only have a role as an adjunct in preventing atopic dermatitis. If you are thinking of taking them, talk to a health professional first.
Respiratory measures: reducing contact with allergens
Respiratory measures aim to reduce contact with allergenic agents:
- Pets: do not let them into the bedroom, wash them regularly and, if possible, groom them outdoors, as the NHS recommends.
- Materials that collect dust, dust mites and mould: upholstered furniture, mattresses, rugs and curtains encourage dust mites to build up, so cutting down on these materials may help. Dusting with a damp cloth and keeping your home dry and well ventilated, dealing with any damp and condensation, helps prevent mould.
- Pollen: in cases of severe reactivity, plan your outings according to the pollen forecast from the Rede Portuguesa de Aerobiologia (for example, for Lisbon: https://www.rpaerobiologia.com/previsao-polinica/lisboa) or the Red Española de Aerobiología (https://www.uco.es/rea/?page_id=262). On days with the highest concentrations, keep doors and windows closed and, according to the NHS, shower and change your clothes after being outdoors.
- Dust mites and dust: wash bedding regularly at 60 °C or above, as the NHS recommends, and vacuum with a vacuum system with high-efficiency filtration, which traps dust instead of releasing it back into the air. You can also opt for mattresses and hypoallergenic pillows, or ones with anti-dust mite covers.
- Indoor air quality: as well as reducing sources of pollution and ventilating your home, you can use an air purifier certified as a medical device. According to the EPA, portable air cleaners with a HEPA filter remove particles from the air, including fine particles, and several studies have found improvements in some allergy or asthma symptoms, although not always major ones.
- Nasal hygiene: rinse your nose with saline solution, which helps clean the nasal passages and gives immediate, though short-lived, relief from symptoms such as a blocked or itchy nose.
The importance of the first years of life
Some studies link two early-life circumstances to a lower risk of allergic disease. A meta-analysis linked birth by caesarean section to a moderate increase in the risk of allergic rhinitis compared with vaginal birth, and a systematic review found evidence, still weak, that longer breastfeeding is associated with a lower risk of allergic rhinitis up to the age of 5.
According to the authors of the meta-analysis, caesarean section accounts for only a small proportion of cases. The type of birth always depends on clinical criteria and should be decided with the healthcare team.
In addition to preventive measures, allergic rhinitis treatment with medication may be needed.
Allergic rhinitis treatment: what are the options?
In general terms, and according to the review in the Revista Portuguesa de Imunoalergologia, treatment for allergic rhinitis is based on environmental control measures, drug therapy and, in selected cases, allergen immunotherapy.
Environmental control measures
Environmental control measures, or avoidance measures, are strategies to minimise exposure to allergens and correspond to the preventive measures described in the previous section.
The EPA states that air filtration can be an effective supplement to reducing sources of pollution and to ventilation, although no air cleaner removes all pollutants. In homes in urban areas or in environments with a lot of airborne particles, an air purifier can therefore complement the other measures.
Medicines for allergic rhinitis
Several groups of medicines are used in the treatment of allergic rhinitis. The most common are:
- Antihistamines: they reduce the action of histamine, the main mediator released during the allergic reaction, which triggers the early symptoms of allergic rhinitis. They can be taken orally or used as a nasal spray and are most effective at reducing sneezing, runny nose and itching of the nose and eyes. Caution: they can cause drowsiness and reduced co-ordination, especially the older, first-generation ones; that is why second-generation antihistamines are recommended, as they cause less sedation. If an antihistamine makes you drowsy, do not drive or use machinery.
- Nasal topical glucocorticoids: are considered the mainstay of allergic rhinitis treatment, due to their anti-inflammatory action, and help control the main symptoms: sneezing, itching, runny nose and nasal obstruction. They are recommended as the treatment of choice for allergic rhinitis in both adults and children.
- Nasal decongestants: they help relieve a blocked nose. Nasal sprays should be used for no more than 3 to 5 days, because prolonged use can cause a rebound effect and rhinitis medicamentosa. The NHS also advises against using them for longer than 5 days.
Specific immunotherapy: allergy “vaccines”
Specific allergen immunotherapy, known as “allergy vaccines”, is the only treatment option that modifies the immune mechanism underlying allergic rhinitis. It gradually induces desensitisation to the allergens responsible and is indicated, in selected cases, for the treatment of moderate to severe allergic rhinitis, usually from the age of 5. It should only be given under medical supervision.
Natural remedies for allergic rhinitis
Among the more natural options, nasal rinsing with saline solutions is a complementary measure that provides immediate, though short-lived, relief, especially from a blocked or itchy nose.
Thermal hydrotherapy (treatments with thermal spring water) and sea bathing are sometimes sought as a complement, but scientific evidence of their benefit in allergic rhinitis is still scarce. They do not replace medical treatment.
Important: consult your doctor to choose the most suitable and safest medicines for you.
Frequently asked questions about allergic rhinitis
Can allergic rhinitis be cured?
So far, there is no definitive cure: according to the NHS, there is currently no cure for hay fever, but treatment can ease the symptoms. Specific immunotherapy is the only option that acts on the immune mechanism of the disease and, according to several studies, its effect on symptoms can last even after treatment has ended.
How can you tell allergic rhinitis from a cold?
In allergic rhinitis, itching of the nose and eyes is common, secretions are clear and watery, there is no fever and symptoms last as long as there is contact with the allergen. A cold is a viral infection which, according to the NHS, usually gets better in 1 to 2 weeks and can cause a high temperature, sore throat and tiredness.
Can allergic rhinitis turn into asthma?
Allergic rhinitis and asthma often occur together. In Portugal, according to SPAIC, people with rhinitis had a risk of asthma almost four times higher than people without rhinitis and, when untreated or uncontrolled, rhinitis contributes to more severe and less controlled asthma. That is why it is important to treat it and to watch out for signs such as wheezing, a persistent cough or shortness of breath.
Does an air purifier help relieve allergic rhinitis?
A purifier with a HEPA filter removes airborne particles and can help reduce exposure to them at home. According to the EPA, several studies with portable HEPA air cleaners have found improvements in one or more allergy or asthma symptoms, although not always major ones, and it is advisable to place the unit in the rooms where you spend most time, such as the bedroom. It is a complement to, not a substitute for, medical treatment and regular cleaning of the home.
Allergic rhinitis: the essentials for relieving symptoms
Given the variety of factors that trigger allergic rhinitis, a specific diagnosis is important for appropriate treatment. If you have moderate to severe symptoms, see a doctor who specialises in allergies (an allergist and clinical immunologist) for a more personalised plan.
Our health depends on the lifestyle choices we make consistently every day. With allergic rhinitis, reducing exposure to allergens and following the recommended treatment helps control symptoms which, when uncontrolled, can affect sleep, energy, daily activities and quality of life.
If you want to reduce allergens in the air in your home, discover the FilterQueen Defender purifier or talk to the Filtrarte team to find the most suitable solution for your space.
LOOK AFTER YOUR HEALTH: CHOOSE YOURSELF!
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By the Filtrarte Expert Team
The information in this article is not intended to recommend any treatment for symptoms or diseases. Consult your doctor for specialist advice.
