Allergic Rhinitis
Allergic rhinitis, commonly known as hay fever, is an inflammation of the nasal passages triggered by allergens in the air. It manifests through symptoms such as a runny or stuffy nose, sneezing, itchy and watery eyes, and swelling around the eyes. These symptoms often appear within minutes of allergen exposure and can significantly affect daily activities, including sleep, work, and study.
Signs and Symptoms
The hallmark symptoms of allergic rhinitis include rhinorrhea (excess nasal secretion), itching, sneezing fits, nasal congestion, and obstruction. Other physical findings may include conjunctival swelling and erythema, eyelid swelling with Dennie–Morgan folds, lower eyelid venous stasis (allergic shiners), swollen nasal turbinates, and middle ear effusion. Behavioural signs like the "nasal salute," where individuals wipe or rub their nose with the palm in an upward motion, are also common. Cross-reactivity with certain foods may occur, such as an itchy throat after eating apples or sneezing when peeling potatoes.
Cause
Allergic rhinitis is typically caused by environmental allergens such as pollen, pet hair, dust, or mould. Genetic and environmental factors contribute to the development of allergies. The immune system's overreaction involves IgE antibodies attaching to allergens, triggering the release of inflammatory chemicals like histamine from mast cells.
Pollen-Related Causes
Pollen from wind-pollinated plants, such as trees (birch, cedar), grasses (ryegrass, timothy), and weeds (ragweed, plantain), is a common trigger for allergic rhinitis. The study of pollen dispersion is known as Aerobiology.
Genetic Factors
Genetic predispositions play a significant role in allergic rhinitis. Recent studies have identified loci and genetic pathways, particularly involving the IL-33 gene and its role in the inflammatory response to allergens.
Diagnosis
Diagnosis is typically based on symptoms, skin prick tests, and blood tests for allergen-specific IgE antibodies. However, these tests can yield false positives. Local allergic rhinitis, where only the nose exhibits an allergic reaction without systemic allergies, may require specialised testing.
Classification
Allergic rhinitis can be classified as seasonal, perennial, or episodic. Seasonal allergic rhinitis occurs during pollen seasons, while perennial allergic rhinitis occurs year-round. The condition can also be classified based on severity and persistence of symptoms.
Prevention
Preventative measures focus on avoiding specific allergens. This includes not having pets, avoiding carpets, and keeping homes dry. Growing up on a farm and having multiple siblings may reduce the risk of developing allergic rhinitis.
Treatment
Treatment aims to reduce symptoms through various methods:
Antihistamines
Antihistamines, both oral and nasal, help control symptoms like sneezing and itching. Second- and third-generation antihistamines like cetirizine and loratadine are less likely to cause drowsiness.
Steroids
Intranasal corticosteroids are preferred for persistent symptoms. They are effective and safe but require continuous use for several weeks to build up therapeutic effects.
Other Measures
Second-line treatments include decongestants, cromolyn, leukotriene receptor antagonists, and nasal irrigation. Topical decongestants should not be used long-term due to the risk of rebound nasal congestion.
Allergen Immunotherapy
Allergen immunotherapy involves administering increasing doses of allergens to build long-term tolerance. It can be administered orally or via injections and is the only treatment that alters the disease mechanism.
Alternative Medicine
Currently, there is no strong evidence supporting the efficacy of alternative medicine for allergic rhinitis. Acupuncture has shown some promise but lacks strong evidence for widespread recommendation.
Epidemiology
Allergic rhinitis is the most common type of allergy, affecting 10-30% of people in Western countries annually. It is most prevalent between the ages of twenty and forty.
History
The condition was first accurately described by the 10th-century physician Rhazes. Pollen was identified as the cause in 1859 by Charles Blackley, and the mechanism was determined by Clemens von Pirquet in 1906.
Self-assessment MCQs (single best answer)
What is the common name for allergic rhinitis?
Which of the following is NOT a typical symptom of allergic rhinitis?
What is the primary cause of allergic rhinitis?
Which type of pollen is a common trigger for allergic rhinitis?
What type of test is commonly used to diagnose allergic rhinitis?
Which treatment method involves administering increasing doses of allergens to build long-term tolerance?
Which of the following is a second- or third-generation antihistamine?
What is the term for the immune system’s overreaction involving IgE antibodies and histamine release?
Which preventive measure is NOT recommended for allergic rhinitis?
Who first accurately described the condition of allergic rhinitis?
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