Allergies explained
Allergies explained
About allergies
An allergy occurs when the body overreacts to an allergen or ‘trigger’ that is typically harmless to most people. Examples of
allergies
include:
hay fever (allergic rhinitis)
asthma
eczema
hives (urticaria)
food allergy
.
The symptoms of allergy range from mild to severe. The most severe type of allergic reaction is
anaphylaxis
, which may cause death without prompt administration of adrenaline (epinephrine). For mild allergies, effective treatments are available to manage or treat allergy symptoms.
Symptoms of allergies
Symptoms depend on the allergy, but may include:
swelling of lips, face, eyes
sneezing
runny nose
red, watery and itchy eyes
wheeze or persistent cough
breathing problems
swelling tongue and tightness of throat
headache
skin rash
abdominal pain (
insect allergy
)
vomiting (insect allergy).
Do not self-diagnose. The symptoms and signs of allergies are common to many other medical conditions. It is important to see your doctor or clinical immunology/allergy specialist for professional diagnosis, management and treatment.
Common allergens
A substance in the environment that can cause an allergic reaction in susceptible people is called an ‘allergen’. There are many different allergens, but they all share one thing in common – protein. Some allergens don’t contain protein to begin with, but bind with protein once inside the body to provoke the allergic reaction.
Common allergens include:
food
– such as
crustaceans
,
eggs
,
fish
,
milk
,
peanuts, tree nuts (for example, almonds, cashews, pecans and walnuts), sesame
and soy products
plants
–
pollen
from grasses and plants
medicines
– including prescription medications (such as penicillin), over-the-counter medicines (such as aspirin) and herbal preparations
insects
– such as
dust mites
and the venom from bees, ticks, ants and wasps
moulds
– such as mushroom and mould spores
animal dander
– such as the fur and skin flakes from domestic pets such as cats and dogs
chemicals
– including industrial and
household chemicals
and chemical products such as
latex rubber
.
The immune system reaction
Allergy is the result of mistaken identity. An allergen enters the body and is wrongly identified by the
immune system
as a dangerous substance. In response, the immune system makes antibodies to attack the allergen. These are specific antibodies of the IgE (immunoglobulin E) class.
When an allergen is found, IgE antibodies trigger a cascade of immune system reactions, including the release of chemicals known as mast cell chemicals. These are substances that the body normally uses to destroy micro-organisms. The most common of these is histamine.
In small amounts, histamine causes itching and reddening of the local area. In large amounts, the nearby blood vessels become dilated and the area swells with accumulated fluid.
The immune system’s tendency to overreact to a harmless substance is thought to be genetic. The term ‘atopy’ describes this genetic tendency. Doctors and clinical immunology/allergy specialists describe a person who has an allergy as being ‘atopic’ – such people usually have raised levels of IgE in their blood.
Where to get help
Your
GP (doctor)
NURSE-ON-CALL
Tel.
1300 60 60 24
– for expert health information and advice (24 hours, 7 days)
Australasian Society of Clinical Immunology and Allergy
(ASCIA)
External Link
What is
allergy?
External Link
Locate a
specialist
External Link
Allergy & Anaphylaxis
Australia
External Link
Dermatologist
Nutrition Australia (Victorian
Division)
External Link
Tel.
(03) 8341 5800
Dietitians
Australia
External Link
Tel.
1800 812 942
Asthma
Australia
External Link
Tel.
1800 278 462