Allergic rhinitis is a chronic inflammatory disease of the upper
airway caused by IgE sensitization to airborne allergens in genetically
susceptible individuals. In the United States, symptoms of allergic
rhinoconjunctivitis (ARC) affect between 20% to 30% of
adults and as many as 40% of children. The clinical presentation
characteristically is associated with frequent sneezing, nasal congestion,
and nasal discharge. The vast majority of patients with allergic
rhinitis complain or display ocular symptoms (ie, itchy/watery
eyes), thus it is termed allergic rhinoconjunctivitis, for
which it is better known. Involvement of the lower airway is frequent: up
to 40% of patients with ARC also suffer from asthma, and
most show evidence of bronchial hyperreactivity. Allergic rhinitis
can affect the child’s quality of life and can be associated
with conditions such as sleep disturbances and learning difficulties.
Allergic rhinitis has been subdivided into seasonaland
perennial types based on time and duration of symptom occurrence.
Seasonal symptoms that only occur in spring and summer are often
referred to as classical hay fever (pollinosis), whereas perennial
allergic rhinitis is caused by an allergic response to allergens
such as dust mites and pet dander that are present throughout the
There is a wide variation in the prevalence of allergic rhinoconjunctivitis
(ARC) worldwide.1 In the pediatric age, the numbers
range from 0.8% to 14.9% in 6 to 7 year olds and
from 1.4% to 39.7% in 13 to 14 year olds. The
reasons behind these disparities are not completely understood, but
both environmental and genetic factors are likely to play a role.
Like other allergic diseases, the prevalence of ARC seems to be
on the rise, particularly in industrialized countries, and as such,
ARC has been named a “disease of civilization.” Risks
factors for allergic rhinitis include family history of atopy, higher
socienoconomic class, and evidence of sensitization.
Aeroallergen sensitization may occur within the first 2 years
of life, especially in children with a family history of atopy,
but classical symptoms of seasonal allergic rhinitis generally do
not develop until 2 to 7 years of age.
In childhood, allergic rhinitis is more frequent in boys, but
in adults it is more frequent in women. The prevalence of seasonal
allergic rhinitis is higher in children and adolescents, whereas
perennial allergic rhinitis has a higher prevalence in adults.
The pathogenesis of allergic rhinoconjunctivitis (ARC) responds
to the same immune mechanisms as other allergic disorders. In this case,
exposure to airborne allergens, in a genetically susceptible individual,
initiates the series of events that lead to the local activation of
allergen-specific T cells with a TH2 bias that direct the production
of inflammatory cytokines, chemokines, and allergen-specific IgE.3 Upon
reexposure to the same allergen, cross-liking of FceR-bound IgE
on the surface of mast cells triggers the release of preformed mediators.
Histamine released by mast cells is largely responsible for the
immediate symptoms associated with ARC such as sneezing, itching, ...