Hay fever, asthma and eczema are more common than ever before. Such
allergies can cause real discomfort and inconvenience. However, the latest
research is uncovering new treatments - and possible cures.
An allergy is a sensitivity to a substance which does not normally cause
discomfort or harm. Allergies can affect almost any part of the body and are
caused by a vast range of natural and artificial substances.
CAUSES OF ALLERGIES
Substances that trigger the symptoms of an allergy are known as allergens.
These can include foods, pollen, spores, insect bites, animal fluff, certain
chemicals, drugs and house dust mites. Some people are even 'allergic' to
heat or cold.
In many cases, it's possible to identify allergens which trigger the
condition - either in food or in substances which come into contact with the
skin - but sometimes they are difficult or impossible to detect. It's still
not known exactly why some of us are prone to allergies.
They do tend to run in families, and a genetic background boosts your
risk fourfold. This link may be due to inherited 'pro-allergy' genes, but
environmental influences are important, too.
THE IMMUNE SYSTEM
Allergies develop when the immune system, which defends our bodies against
disease, overreacts to a normally harmless substance.
White blood cells (lymphocytes) produced by our immune system are
constantly on the look-out for foreign substances such as viruses, bacteria
and foreign proteins.
The immune system of a healthy person recognizes the difference between a
foreign protein like a virus and a harmless one, such as a food protein.
ROLE OF MAST CELLS
In people prone to allergies, for reasons not fully understood, the immune
system reacts to harmless proteins as if they were dangerous. The white
blood cells change into plasma cells, which create antibodies when an
allergen is present. The antibodies are thought to attach themselves to
special cells called mast cells, which contain a number of chemicals
The next time the body encounters those proteins, the antibodies combine
with the foreign proteins and tries to neutralize them. This triggers the
break-up of the mast cells, which fall apart and release the chemicals into
These chemicals are responsible for a whole range of allergic reactions,
such as redness, itching, and swelling of nasal passages, as well as the
stuffy nose of hay fever and the itchy weals of urticaria. Other common
allergic reactions include narrowing of the muscles in the airways, evident
in asthma, and the production of excess nasal fluid seen in hay fever.
Allergic symptoms tend to show up in the parts of the body which are
exposed to the allergen. An airborne allergen, like pollen, affects the
eyes, nose and air passages; food allergies reveal themselves through
swollen lips, diarrhoea or stomach upsets, while allergies to metal and
rubber will usually result in skin rashes.
However, if an allergen gets into the bloodstream, it can cause reactions
almost anywhere in the body. This is particularly true of food allergens,
which are absorbed into the bloodstream through the digestive system.
Eczema, the most common form of skin allergy, appears as a rash or area of
scaly skin that is found mostly on the hands, face, neck and in the creases
of the forearms and behind the knees. The inherited type, atopic eczema, is
especially common in babies and children.
Contact eczema, or dermatitis, which often affects adults, is caused by
direct skin contact with certain allergens. It often affects the hands and
can be caused by soaps, detergents, washing powders, glues or other
substances or chemicals encountered at work.
Some people are allergic to nickel, found in costume jewellery and
fastenings on bras or jeans. A red blistery rash develops where the nickel
is in contact with the skin.
Urticaria is often called nettle-rash because the red itchy weals
resemble nettle stings. The rash usually appears suddenly, and may affect
just a small area. However, in severe cases it can cover the whole body.
Foods, drugs, perfumes and even exposure to heat and cold can all be to
The main target of hay fever, or seasonal rhinitis, is the nose, but it can
also affect the eyes and ears. Unlike a common cold, which usually lasts for
only a few days up to a week, hay fever lasts for as long as you are exposed
to the pollen to which you are allergic.
Some people suffer symptoms similar to hay fever all year round. They
have a stuffy, runny nose virtually all the time, which is often worse when
indoors, particularly at night and in the early morning. This condition,
called perennial rhinitis, is often the result of an allergy to the house
THE FOOD CONNECTION
The most obvious symptoms of an acute food allergy are digestive
disturbances like nausea, diarrhoea, or vomiting, but there may be other
symptoms such as skin rashes, or a swollen tongue or lips.
These symptoms - usually with the exception of skin rashes - come on
almost immediately after eating the allergen, which makes it quite easy to
identify the culprit.
Evidence shows that conditions such as irritable bowel syndrome, colic in
babies and asthma attacks can all be food-related.
More controversial is the idea that food allergies lie behind a much
wider range of conditions, both physical and emotional. These include
depression and anxiety, migraine, headaches, schizophrenia and hyperactivity
If you suspect you have an allergy, see your doctor. If necessary, he can
refer you to a special allergy clinic. You may be asked to keep a diary,
detailing your symptoms and any allergens you've been exposed to over a
period of months.
You may be given a skin prick test. This can involve dropping a watery
solution containing a small amount of a particular allergen onto your
forearm, and pricking the skin so that some of the allergen enters your
system. If you are allergic to that substance, a round, red weal appears
within about 15 minutes.
Nasal allergies are sometimes diagnosed using a 'challenge' test.
Allergens are sprayed into your nose, inhaled and then exhaled to determine
if a reaction occurs.
A patch test may help show up skin allergies. Special patches are
impregnated with various allergens and then applied to your skin, usually on
your back. The patches are left on for at least a couple of days before a
reaction appears. Blood tests, which involve measuring the amount of allergy
antibody in the blood, may also be carried out.
A special elimination diet, which involves first cutting out and then
reintroducing suspect foods to see if they cause a reaction, may be used
both to identify the cause of a food allergy and to treat it.
Antihistamines - which block the activity of histamine - are useful for
relieving the symptoms of allergies such as hay fever, urticaria, and
Drugs like sodium cromoglycate work by preventing mast cells from
exploding. They can be used for asthma and other nasal allergies and, in
some cases, for food allergies. Other drugs include corticosteroids, which
mimic the action of anti-inflammatory hormones.
Desensitization involves injecting small quantities of an allergen over a
period of time to build up immunity. Though not often carried out by the
doctor, this may be tried if drug treatment is ineffective.