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Allergic rhinitis update (Review/Guideline, Lancet)
Allergic rhinitis is mostly just an annoyance for 400 million people worldwide, but the condition can predispose to frequent upper respiratory infections, and worsen asthma; Alexander Greiner et al tell you what you need to know in this review in Lancet.
Incidence peaks in the teenage years.
The nasal inflammation of allergic rhinitis synergizes with inflammation from infections, so people with allergic rhinitis get more colds, which may be more severe or prolonged.
Moderate-to-severe allergic rhinitis is associated with poor asthma control; rhinitis should be treated in people with asthma (a high proportion of whom have allergic rhinitis).
The Allergic Rhinitis and its Impact on Asthma 2008 guideline can help guide treatment, but like most such guidelines, it's 160 pages long and too cumbersome to access routinely.
These authors advise that skin testing or serum testing identifying allergen-specific IgE are necessary to make the diagnosis of allergic rhinitis. This sounds costly and infeasible for a condition affecting 400 million people, but I can't back that up with a formal analysis.
Nasal-specific IgE production, a process called entopy, may occur and be missed by standard allergen testing such as skin testing or serum (RAST) testing.
Churg-Strauss, Wegener's granulomatosis, and sarcoidosis can mimic allergic rhinitis or coexist with it, although of course they're far more rare.
For treatment of allergic rhinitis:
For mild disease, authors recommend only oral or topical non-sedating antihistamines.
For moderate-to-severe allergic rhinitis, intranasal corticosteroids are the most effective treatment. Interestingly, intranasal steroids have not yet been shown to improve asthma in people with coexisting allergic rhinitis in prospective studies.
Immunotherapy is also effective, and may prevent the development of asthma in children. However, immunotherapy carries about 1 in 1,000 risk of anaphylactoid reactions. Therefore, immunotherapy should be reserved for those whose symptoms are predominantly due to one allergen on allergy testing.
Other established focused treatments include:
Nasal iptratropium for watery rhinorrhea
Leukotriene inhibitors for asthmatics with cough
Surgical referral for those with refractory allergic rhinitis, who may have chronic infection or a structural problem (blockage).
Greiner AN et al. Allergic rhinitis. Seminar. Lancet 2011;378:2112-2122.