Australian Doctor Australia Doctor 18th August 2017 | Page 22

How to Treat – Allergic rhinitis
from page 20
persistent rhinitis, most likely due
to multiple pollen sensitivities or
sensitivities to other indoor aller-
gens. Likewise, a large number of
patients sensitive to house dust
mites experience a mild intermit-
tent allergic rhinitis. 8
Inhaled aeroallergens have a
significant geographic and sea-
sonal variation so it is important
for practitioners to understand
their region’s prominent aller-
gens.
House dust mites
The most important species, Der-
matophagoides pteronyssinus, D.
farinae and Euroglyphus maynei
feed on human skin dander, plen-
tiful in mattresses, sheets, pillows,
toys and furniture. They prefer
humid (>50%), warm (>20°C)
environments. House dust mite
allergens are found in mite faeces,
made airborne when contami-
nated fabrics are disturbed. These
allergens quickly settle. Higher
concentrations of mites are asso-
ciated with an increased risk of
developing asthma at a later date. 8
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 environ-
ments for many months. The
principal dog allergen is found in
the hair, saliva, skin and urine.
Pollens
Aerodynamic, wind-borne (ane-
mophilous) pollens are the most
common allergens in patients
with allergic rhinitis, and may
travel many hundreds of kilo-
metres from the pollen source.
Insect-carried
(entomophilous)
pollens such as those of Aus-
tralian 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 com-
mon tree allergens in Australia.
Occupational allergens
Patients may be exposed to a very
wide variety of potential aller-
gens in the workplace. Allergens
commonly implicated in aller-
gic rhinitis and asthma include
natural latex, laboratory animal
dander, flours and grains in bak-
eries as well as a large number of
compounds and chemical inter-
mediates used in plastics manu-
facturing. 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 aller-
gic rhinitis and asthma has long
been observed by practitioners
and has, more recently, been the
subject of several large, epide-
miological studies. These studies
demonstrated that nasal symp-
toms were reported in up to 78%
of patients with asthma and up to
38% of patients with allergic rhi-
nitis 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 Tas-
manian 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:
• Rhinitis, independent of aetiol-
ogy, is a risk factor for asthma;
• Adults and children with con-
comitant allergic rhinitis have
more asthma-related hospitali-
sations 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, warm-
ing and humidification, filtering
Galen, 2nd century AD
“THE apertures of the nose, how
marvellously they come next after
the spongelike (ethmoid) bone…
and how the connection was cut
through into the mouth at the
palate in order that