Allergies are essentially caused by the immune system identifying a particular substance as being harmful to the body, even when the substance is in fact harmless. Respiratory allergies refer to allergic reactions that are triggered by an allergen that is inhaled.
Inflammation of the lining in the nose and nasal passage, allergic rhinitis is one of the symptoms of respiratory allergies. “Allergic rhinitis shares many features with allergic asthma,” Giuliano Molinari et al. explained in Respiratory Allergies: A General Overview of Remedies, Delivery Systems, and the Need to Progress (published in ISRN Allergy). The authors cautioned that allergic rhinitis is also often associated with sinusitis or other comorbidities such as conjunctivitis and precedes allergic asthma.
To understand respiratory allergies you need to recognise the many different substances that can trigger allergic symptoms. According to Chacko Allergy, Asthma, and Sinus Centre, the most common allergens include:
- Pollen is a microscopic particle released into the air by trees, grasses, weeds, and flowers.
- Dust mites are microscopic insects that live in dust or fibres within the home, such as pillows, mattresses, carpets, and upholstery. If someone is allergic to dust mites, they may have symptoms like those of pollen allergies, as well as wheezing and coughing, which are symptoms associated with asthma.
- Mould is a fungi with spores that release into the air. Mould is found in damp areas.
- Animal/pet dander is the proteins that are released by an animals’ sweat glands that are in the animal’s skin, which is shed in dander. Proteins in an animal’s saliva can also cause allergic reactions in some people.
Allergic rhinitis symptoms include blocked nose, itchy or runny nose, sneezing, red and itchy eyes, unusual sounds such as persistent sniffing, snorting, or clicking noises, an itchy throat and/or ears, and trouble sleeping.
“This is not a trivial disease,” cautioned the SA Allergy Foundation. “It is a major cause of failure to learn. Inadequate control of allergic rhinitis has been proven to reduce school achievement, with sedating antihistamines exacerbating the learning disability, but treatment with intranasal steroids and second-generation antihistamines can abolish it. Allergic rhinitis occurs in 20-30% of the population, and as many as 40% may also have asthma, often undiagnosed.
Six classes of drug and nasal saline are used to treat allergic rhinitis, according to Molinari et al. “Oral and topical H1-antihistamines, intranasal glucocorticosteroids, mast cell stabilisers, decongestants, anticholinergic agents, and leukotriene inhibitors, also called antileukotrienes.” While allergic rhinitis medications are typically administered orally or intranasally, “the intranasal route allows higher concentrations of the drug to be delivered, thus minimising systemic side effects.”
“Several antihistaminic preparations are available on the market: oral antihistamines (tablets and drops), nasal sprays that can act more rapidly than oral preparations, and eye drops. They are often produced in combination with other drugs such as mast cell stabilisers and decongestants,” the researchers said.
Molinari et al. recommend intranasal corticosteroids as the first-line treatment for moderate, severe, or persistent allergic rhinitis. “Intranasal corticosteroids target the inflammatory mechanism of the early and late phases of allergic processes and are therefore effective in treating most symptoms of allergic rhinitis including congestion, sneezing, rhinorrhoea, and nasal pruritus.”
Intranasal mast cell stabilisers
Generally not as effective as antihistamines or INCs, mast cell stabilisers have no direct anti-inflammatory or antihistaminic effects and minimal bronchodilator effects, however, they are effective for prophylaxis.
Causing vasoconstriction, decongestants relieve oedema and congestion of the nasal mucosa but do not alleviate nasal itching, sneezing, or rhinorrhoea associated with allergic rhinitis. Intranasal decongestants are often associated with a corticosteroid or an antihistamine to improve the delivery of these drugs.
Intranasal anticholinergics may reduce rhinorrhoea by inhibiting serous and seromucous gland secretions locally.
Studies have found that leukotriene receptor antagonists are more effective in improving night-time symptoms but less effective in improving daytime nasal symptoms compared to antihistamines.
“Evidence shows that nasal saline is beneficial in treating nasal allergic rhinitis symptoms, particularly, during pregnancy, and in children and patients who are run down, as it is associated with few adverse effects,” Molinari et al. concluded.