What is an allergy?
Allergic disorders, including anaphylaxis, allergic rhinitis/hayfever, eczema, and asthma, affect approximately 25% of people in the developed world1
An allergy is an excessive or abnormal adaptive immune response directed against non‐infectious, often inert environmental substances (allergens), including non‐infectious components of certain infectious organisms1. For people with allergies, persistent or repetitive exposure to allergens, which are typically innocuous substances, results in chronic allergic inflammation1.
In turn, this can produce long‐term changes in the structure of the affected organs and substantial abnormalities in their function1.
Allergens and allergic inflammation:
There are two main types of allergen:
1. Any non‐infectious environmental substance that can induce immunoglobulin E (IgE) production (thereby ‘sensitising’ the subject) so that later re‐exposure induces an allergic reaction1.
Common allergen sources include1:
- Grass and tree pollens
- Animal dander (from skin and fur)
- House dust mite faecal particles
- Certain foods (eg, peanuts, tree nuts, fish, shellfish, milk, and eggs)
- Various medicines
- Insect venoms
2. A non‐infectious environmental substance that can induce an adaptive immune response linked to local inflammation—but one thought to occur independently of IgE (eg, allergic contact dermatitis to poison ivy or nickel)1.
This is the inflammation produced in sensitised subjects after exposure to a specific allergen(s). With persistent or repetitive exposure to allergens, chronic allergic inflammation develops, with associated tissue alterations1.
What is allergic rhinitis?
Allergic rhinitis (AR) is defined as an IgE antibody‐mediated, inflammatory disease characterised by one or more of the following symptoms2:
- Nasal congestion
- Rhinorrhea—runny nose (anterior and posterior)
- Sneezing and itching
There are several AR classification characteristics that can be helpful to determine appropriate patient treatment strategies, including2:
1. Temporal pattern and context of exposure to a triggering allergen:
a). Seasonal (e.g., pollens) or perennial (year‐round exposures such as house dust mites),
b). Episodic environmental (from allergen exposures not normally encountered in the patient’s home or occupational environment, e.g. visiting a home with pets not present in an individual’s home)
2. Frequency and duration of symptoms
3. Severity of symptoms
AR has traditionally been categorised as seasonal AR (SAR) or perennial AR (PAR), both of which are conditions recognised as having similar pathophysiologic and end‐organ manifestations. In general, the differences between the two conditions are primarily based on the causes and duration of disease2.
What happens when an allergen infiltrates the body?
The body’s immune response to allergens includes a series of early‐ and late‐phase reactions – the allergic cascade. There are several allergic mediators involved in this cascade, not just histamines3.
Typically, the allergic cascade follows this pattern3,4:
- Sensitisation to an allergen
- Early‐phase response upon re‐exposure to an allergen
- Late‐phase response
When the body is exposed to an allergen:
- Sensitisation involves being exposed to an allergen for the first time3
- The body produces immunoglobulin E (IgE) designed specifically for that particular allergen, but an allergic reaction does not yet occur3
- Re‐exposure to an allergen triggers an early‐phase response that occurs within minutes to an hour3
- The IgE of mast cells binds to the allergen, crosslinking the IgE3
- When enough crosslinking occurs, the mast cells explode with histamine and other inflammatory substances, called mediators, such as cytokines, leukotrienes, prostaglandins, eosinophils, and thromboxanes3,4
- The end result is the allergic response consisting of a range of symptoms such as rhinorrhea (runny nose), sneezing, congestion, and pruritus (itching)3
- The late‐phase response occurs from 3 to 10 hours after allergen re‐exposure3
- Immune cells, such as eosinophils, secrete substances that increase inflammation and bring other immune cells into the reaction, perpetuating the inflammatory response3
- Symptoms can be more severe than those in the early phase3
MOA of antihistamines
Antihistamines work by binding to the H1 receptor, therefore inhibiting histamine (a mediator of the inflammatory response) from binding to the H1 receptor. This hinders the body’s response when exposed to an allergen, thus preventing symptoms such as wheezing, sneezing, coughing, itchy nose and eyes, runny nose, and shortness of breath5.
MOA of decongestants
Decongestants work by stimulating receptors on blood vessels, causing vasoconstriction and shrinking of the nasal turbinates. Constriction alleviates nasal mucosa inflammation and allows the sinuses to drain, thereby reducing nasal congestion6.
MOA of anti‐leukotrienes
Anti‐leukotrienes block the action of leukotrienes, which cause tightening of airway muscles and production of excess mucus and fluid, reducing nasal secretions7.
MOA of intranasal corticosteroids (INSs)
INSs, often used as first‐line treatment for patients with mild persistent or moderate‐to‐severe symptoms, work locally in the nasal mucosa to block multiple mediators involved in the allergic cascade, including histamine, cytokines, leukotrienes, chemokines, prostaglandins, and tryptase4,8-10.
- Act on both early and late phases of the inflammation process, therefore relieving the symptoms they cause
- Provide relief of nasal congestion and itching, runny nose and sneezing, and itchy, watery eyes.
Where are allergens found?
Where are patients encountering these allergens? Some allergens are more obvious than others.
Some common allergens are11:
- Tree, grass, and weed pollen
- Dust mites
- Animal dander
Some less obvious allergens are12:
- Garden leaf piles
In addition to oral antihistamines and intranasal corticosteroids, first‐line treatment for allergies also involves the avoidance of triggers that may cause an allergic reaction13.
Avoidance strategies include13:
- Use of allergen‐impermeable covers for bedding
- Maintaining relative humidity in the home below 50% to inhibit mite growth
- Reducing pollen exposure by keeping windows closed, using air conditioning, and limiting the amount of time spent outside during peak pollen season
- Avoiding exposure to or ownership of pets
Unfortunately, while avoidance is ideal, it is not always realistic.
Prevalence of allergic rhinitis (AR)
Allergic rhinitis is a global health problem, affecting up to 20% of people globally14.
44% of British adults suffer from at least one allergy, a statistic that is on the rise15 and AR affects up to 40% of British children15.
The symptoms of AR can have a deep impact on an individual’s emotional and psychological well‐being. Patients may be looking for a solution that restores their ability to live their lives uninterrupted by AR symptoms.
AR may limit the ability of your patients to participate in social and outdoor activities, work productively, and sleep16.
Recent studies indicate that the prevalence of AR is increasing17. Across the United States and Europe, in many populations, the frequency of sensitisation to inhalant allergens is increasing and is now more than 40%18.
Quality of life impact
Many patients will “suffer in silence” without talking about their symptoms. They may be purposefully diminishing their allergy symptoms and the impact they have on their quality of life for a variety of reasons19:
- They believe allergies aren’t that serious or are not a “real disease,” but more of a nuisance20
- They may not know that while allergies may seem benign, they can still significantly impact their quality of life19
- They may be unaware that untreated allergies can increase the risk for more serious diseases, such as anaphylaxis, asthma, sinusitis, altered mood, and cognitive impairment19,21
Patients may not recognise some symptoms as being related to allergies. In addition to the more obvious symptoms, these surprising symptoms may be due to allergies19,21,22:
- Chronic fatigue
- Upper respiratory infection
- Sinus infection
- Sleeping problems
- Difficulty concentrating
- Lack of exercise endurance