Allergies are one of the most common causes of illness,
estimated to affect up to 1 in 5 people, and they are becoming more common around the world.
Allergy occurs when our body becomes sensitive to a substance,
called an allergen, that is harmless to most people.
For example, common allergens include: Pollen (which causes hayfever), certain foods (such
as nuts, milk and eggs), Insect bites (such as bee and wasp stings), Dust mites, Moulds,
Animal fur, some medicines, and certain materials (such as latex).
So how do allergies occur?
The immune system is how our body detects, remembers and eliminates foreign material that is
harmful to the body, such as viruses and bacteria, and allergens are treated in the same way.
When first exposed to an allergen, the immune system creates a type of protein
called an IgE antibody that is able to uniquely recognise that allergen.
After this exposure the antibodies lie in wait on a type of immune cell called Mast cells.
If the allergen is encountered again, it causes an allergic reaction. The allergen
binds to the antibodies, triggering the Mast cells to release their contents,
including chemical messengers, such as histamine. These have a range of effects on the body.
Common symptoms triggered by this reaction include: Itchy skin, rash or swelling,
Sneezing and runny nose, Inflammation and congestion around the nose and eyes,
Cough and wheeze, Diarrhoea or feeling sick.
These symptoms might be mild and occur over a period of time,
but allergic reactions can also happen straight away.
For some types of allergies, reactions can be severe and life-threatening – called anaphylaxis.
In anaphylaxis, an extreme reaction of the immune system leads the blood vessels to widen and become
leaky, dangerously lowering blood pressure. The eyelids, lips, or throat can swell up,
and the airways can tighten, leading to difficulty breathing. Other effects may include anxiety,
tummy cramps, vomiting, diarrhoea, drowsiness, and loss of conciousness.
Anaphylaxis is a medical emergency that can be fatal if not treated promptly, so it important
to seek help immediately. Some people who have had an anaphylactic reaction before might carry
an adrenaline auto-injector pen, prescribed by their doctor. This can be used whilst awaiting
further medical help, and is easy to use, with the instructions on the side. It is important
to go to hospital, even if you feel better, for a period of observation in case symptoms return.
Here, further supportive treatments and medicines can be given if required.
How are allergies diagnosed? When and where symptoms occur can provide clues, if these follow
exposure to a particular allergen. As well as symptom history, family history is also relevant,
as some families have a genetic tendency to develop allergic diseases, called ‘atopy’.
Allergy testing is also sometimes used to investigate further or confirm an allergy.
These include blood tests for total and specific IgE antibodies,
and skin prick or patch testing, where tiny amounts of different
allergens are introduced to the skin in a safe way, to see if the skin reacts.
If an allergy is diagnosed, there are many ways of reducing its impact. Firstly,
it is important to try to avoid the allergen as much as possible. Medications are also available
to help with symptoms. Antihistamines and steroids directly dampen down the allergic response.
Other medications can provide symptom relief, such as skin creams or decongestants.
If an adrenaline pen is prescribed, it should be carried at all times, as it’s not always possible
to avoid allergens. It’s also important that allergies are recorded on your medical records.
Some allergies can also be cured through immunotherapy. This involves being exposed
to a tiny amount of allergen in a safe and controlled way, and giving larger and
larger doses over time so that the body gradually becomes desensitised to it.
Allergies are very common in childhood, and can be lifelong, though for many, allergies fade as
they get older. While allergies can be disruptive and impact on quality of life, they can usually be
managed through allergen avoidance, treatment and preparation. It is important for everyone, family
and friends, and wider society, to be mindful of allergies and the risks they pose to some people.
We hope this HealthSketch has been useful to you, and those around you
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