Dec
2018
23
F
Cr
Feature Review
Clinical
Animal dander
Cat allergens are produced in sebaceous glands,
saliva and anal glands. Their main reservoir is
the fur, from where these allergens can become
airborne for long periods of time, contaminating
environments for many months. The principal
dog allergen is found in the hair, saliva, skin and
urine.
Pollens
Aerodynamic, wind-borne (anemophilous)
pollens are the most common allergens in
patients with allergic rhinitis, and may travel
many hundreds of kilometres from the pollen
source.
Insect-carried (entomophilous) pollens,
such as those of Australian wattles, are too
heavy to remain airborne for long enough to be
troublesome except to those in direct contact
with them (for example agricultural or insect
workers and florists). 3
Trees tend to pollinate at the end of winter
and early spring. Pollens of the silver birch, olive
tree, English oak and Murray pine are common
tree allergens in Australia.
Occupational allergens
Patients may be exposed to a very wide variety
of potential allergens in the workplace.
Allergens commonly implicated in allergic
rhinitis and asthma include natural latex,
laboratory animal dander, flours and grains
in bakeries, as well as a large number of
compounds and chemical intermediates used in
plastics manufacturing.
A patient’s current and previous
occupational exposures are therefore a key
element in the history.
The united airway hypothesis –
allergic rhinitis and asthma
A relationship between allergic rhinitis and
asthma has long been observed by practitioners
and has, more recently, been the subject of
several large, epidemiological studies. These
studies demonstrated that nasal symptoms were
reported in up to 78% of patients with asthma
and up to 38% of patients with allergic rhinitis
might have asthma. 9
A temporal relationship exists between
allergic rhinitis and asthma; the majority of
patients with allergic rhinitis and asthma had
symptoms of rhinitis first or were diagnosed
with both diseases within one year of each
other. 9
Analysis of data from the Tasmanian
Asthma Study found that childhood allergic
rhinitis confers a two- to sevenfold increase
in the risk of incident asthma in later life, and
a threefold risk of persistence of asthma to
middle age. 1
The ARIA 2008 Update makes the following
points regarding this relationship:
Figure 3. Dennie–Morgan lines.
• Rhinitis, independent of aetiology, is a risk
factor for asthma;
• Adults and children with concomitant
allergic rhinitis have more asthma-related
hospitalisations than those with asthma
alone; and
• Patients with allergic rhinitis but
without asthma have greater bronchial
hypersensitivity. 8
Some of this relationship may be explained
by the loss or impairment of the functional
characteristics of the nose that protect the
airway in nasal obstruction — that is, warming
and humidification, filtering and mucociliary
clearance. Treatment of allergic rhinitis has been
shown to improve asthma symptoms and reduce
bronchial hypersensitivity. 1
It is imperative, therefore, that the condition
is promptly diagnosed and properly managed
to reduce the risk of patients developing asthma
and/or to reduce its severity.
DIAGNOSIS AND INVESTIGATION
Diagnostic approach
There are three key aims in the assessment of
a patient presenting with signs and symptoms
consistent with allergic rhinitis:
1. Establishing the diagnosis (and excluding
other concerning diagnoses);
2. Determining the impact of symptoms; and
3. Assessing the presence and degree of
associated conditions.
History
The approach to the patient presenting with
suspected allergic rhinitis begins with a
thorough history of specific and associated signs
and symptoms, medication use, presence of
associated atopic conditions, and family history.
The cardinal symptoms are bilateral watery
rhinorrhoea, sneezing, nasal pruritis and nasal
obstruction. Conjunctivitis is also a common
complaint.
Patients may report postnasal drip associated
with a posterior rhinorrhoea. Important
features of the history and their significance are
outlined in table 1.
Examination
The face
Examination begins with inspection of the face
where the stigmata of allergic rhinitis are readily
observed. Do not be surprised if the patient
greets you with the ‘allergic salute’.
The ‘nasal crease’ (see figure 2) is a
persistent, transverse line, with altered
pigmentation occurring at the site of the natural
crease formed when the tip of the nose is pushed
upwards (as in the ‘allergic salute’). 12 This crease
is caused by habitual manipulation of the nose.
Dennie–Morgan lines (see figure 3) are crease-
like wrinkles that form under the lower eyelid in
children with allergic rhinitis and other allergic
diseases. ‘Allergic shiners’, or dark circles under
the eyes, (see figure 2) are caused by increased
regional blood flow and vascular permeability.
The eyes
Eye redness, oedema and mucoid discharge
is consistent with a concomitant allergic
conjunctivitis. Conjunctival injection is not
uncommon. Watery discharge may also result
from transient or partial lacrimal obstruction in
allergic rhinitis.