Key Difference – Allergic vs Nonallergic Rhinitis
Rhinitis is the inflammation of the nasal mucosa. It is an upper respiratory tract disorder. Excessive mucus production, congestion, sneezing paroxysm, watery eyes, nasal and vocal pruritus are the clinical symptoms of rhinitis. In allergic rhinitis, the symptoms are triggered by an allergen. In contrast, nonallergic rhinitis is not triggered by an allergen, and there are no associated hypersensitive reactions. This is the key difference between allergic and nonallergic rhinitis.
1. Overview and Key Difference
2. What is Allergic Rhinitis
3. What is Nonallergic Rhinitis
4. Similarities Between Allergic and Nonallergic Rhinitis
5. Side by Side Comparison – Allergic vs Nonallergic Rhinitis in Tabular Form
What is Allergic Rhinitis?
Allergic rhinitis is defined as nasal discharge or blockage and sneezing attacks that last for more than an hour due to an allergen. It can be of two types: seasonal or intermittent rhinitis, which occurs during a limited period of the year, and perennial or persistent rhinitis, which occurs throughout the year.
IgE antibodies are produced against the allergen by the B cells. IgE then binds to the mast cells. This cross-linking leads to the degranulation and the release of chemical mediators such as histamine, prostaglandin, leukotrienes, cytokines and proteases (tryptase, chymase). Acute symptoms like sneezing, pruritus, rhinorrhea and nasal congestion are caused by these mediators. Sneezing may occur within few minutes from the entry of an allergen into the nasal cavity, and it is followed by an increase in the nasal secretions and blockage which are due to the action of histamine. Furthermore, eosinophils, basophils, neutrophils and T lymphocytes are recruited to the site by the antigen presentation to the T cells. These cells cause irritation and edema, resulting in the nasal obstruction.
Seasonal Allergic Rhinitis
Seasonal rhinitis, which is also known as the hay fever, is one of the commonest allergic disorders with prevalence rates exceeding 10% in some parts of the world. Sneezing, nasal irritation and watery nasal secretions are the common clinical features. But some patients may also suffer from itching of the eye, ear, and soft palate.
Tree pollens, grass pollens, and mold spores are the usual culprits that act as the allergens to provoke the immune system. Seasonal allergic rhinitis may occur at different times of the year in different regions, mainly because of the variation in the pattern of pollination.
Perennial Allergic Rhinitis
About 50% of the patients with perennial rhinitis may complain of sneezing or watery rhinorrhea, and others usually complain of nasal blockage. These patients may also have eye and throat symptoms.
Inflammatory mucosal swellings can obstruct the drainage of secretions from the sinuses, leading to sinusitis.
The most common allergen causing perennial allergic rhinitis is the fecal particles of house dust mite, Germatophagoides pteronyssinus or D. farinae, which are invisible to the naked eye. These mites are found in dust all over the house especially in damp places. The highest concentration of mites is found in human beddings. Next commonest allergen is the proteins derived from urine, saliva or skin of domestic pets, especially the cats. Perennial rhinitis makes the nose more responsive to nonspecific stimuli like cigarette smoke, household detergents, strong perfumes, washing powder and traffic fumes.