Perennial allergic rhinitis It's important to treat this chronic condition to avoid long-term damage an interview with Donald F. Stark, MD

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What are the symptoms?
Perennial allergic rhinitis (PAR) is characterized by intermittent or continuous nasal symptoms without any clear-cut variation throughout the year. Because of this, it's often more difficult to diagnose than seasonal allergic rhinoconjunctivitis or typical hay fever. It has the same underlying mechanisms as the seasonal variants, but the allergen exposure is on a more chronic basis, causing continuous or recurring symptoms all year long.

The prevalence of allergic rhinitis, including the seasonal as well as perennial variant, is estimated to be 10-40% of the population, depending on the countries surveyed. It's difficult to determine what fraction of this is due to PAR -- probably because patients often have a combination of both allergic and non-allergic factors contributing to their symptoms.

What are the causes?
The most common triggers for PAR are dust mites, animal danders, moulds or cockroach. Because patients are often exposed to these allergens on a continuous basis, it may not be clear what specific factor is causing symptoms. Some slight seasonal improvement, for example, might be visible due to diminished dust mite exposure during the chilly and dry winter months in most of Canada. Likewise, pets that are kept indoors during the cold season but are going outside in warmer weather may cause exacerbations in winter. The amount of mould spores can also vary in indoor environments, depending on the degree of moisture present or on the ventilation in the house.

Are there other conditions that mimic PAR?
A number of conditions that can mimic PAR are listed in the accompanying table. For example, patients may have a chronically stuffy nose from drug reactions, including topical alpha-adrenergic agonists causing a rebound nasal congestion, alpha-adrenergic blockers, oral estrogens and ophthalmic or oral beta-blockers. These meds can also lead to prominent rhinorrhea symptoms, more correctly termed vasomotor rhinitis. This condition is caused by instability of the neurovascular lining of the nose, triggering episodes of watery nasal discharge. Some patients also have a related condition -- gustatory rhinitis -- where certain hot-temperature or spicy foods trigger acute episodes of watery nasal discharge.

Various infections, particularly chronic sinus infections, tuberculosis, syphilis and fungi might also present with chronic nasal obstruction or rhinorrhea. Under certain circumstances, systemic conditions such as cystic fibrosis and immunodeficiencies, immotile cilia syndrome, hypothyroidism and rhinitis of pregnancy should be considered for differential diagnosis. Structural abnormalities of the nasal passages can be another cause of chronic rhinitis, e.g. septal deviation, concha bullosa, nasal polyps, adenoidal hypertrophy and foreign bodies. Neoplasms such as squamous cell carcinoma in smokers and nasal pharyngeal carcinomas in the Asian population must also be kept in mind. Finally, consider granulomatous diseases such as Wegener's granulomatosis, sarcoidosis and midline granuloma, and remember that atrophic rhinitis may develop in the elderly.

How do you distinguish PAR from other types of rhinitis?
A careful medical history is the mainstay of making any diagnosis. Often, the patient has an atopic background with other conditions such as atopic dermatitis or asthma preceding the development of allergic rhinitis. A family history of atopy also suggests PAR. An individual may volunteer that he or she notices improvement when away from the regular home environment, particularly when travelling to a different geographic area. It can take several days to see improvement away from home -- weekend absences often aren't sufficient to detect a difference.

When you're dealing with allergic rhinitis, examination of the nose will often point towards the diagnosis, as symptoms of congestion usually dominate. You may also notice the pale edematous mucosal appearance of allergic rhinitis as opposed to dry or inflamed-looking mucosa of non-allergic disease. You can check for nasal polyps and other structural abnormalities, such as a septal deformity, by examining the nasal passages. If additional systemic symptoms are present, you may want to consider other illnesses.