What are allergies caused by
Allergies occur when the body’s immune system reacts to a specific substance as though it’s harmful.
It’s not clear why this happens, but most people affected own a family history of allergies or own closely related conditions, such as asthma or eczema.
The number of people with allergies is increasing every year.
The reasons for this are not understood, but 1 of the main theories is it’s the result of living in a cleaner, germ-free environment, which reduces the number of germs our immune system has to deal with.
It’s thought this may cause it to overreact when it comes into contact with harmless substances.
Symptoms of an allergic reaction
Allergic reactions generally happen quickly within a few minutes of exposure to an allergen.
They can cause:
- a runny or blocked nose
- a red, itchy rash
- wheezing and coughing
- red, itchy, watery eyes
- worsening of asthma or eczema symptoms
Most allergic reactions are mild, but occasionally a severe reaction called anaphylaxis or anaphylactic shock can happen.
This is a medical emergency and needs urgent treatment.
Substances that cause allergic reactions are called allergens.
The more common allergens include:
- dust mites
- grass and tree pollen – an allergy to these is known as hay fever (allergic rhinitis)
- latex – used to make some gloves and condoms
- mould – these can release little particles into the air that you can breathe in
- animal dander, tiny flakes of skin or hair
- insect bites and stings
- medicines – including ibuprofen, aspirin and certain antibiotics
- food – particularly nuts, fruit, shellfish, eggs and cows’ milk
- household chemicals – including those in detergents and hair dyes
Most of these allergens are generally harmless to people who are not allergic to them.
Is it an allergy, sensitivity or intolerance?
A reaction produced by the body’s immune system when exposed to a normally harmless substance.
The exaggeration of the normal effects of a substance.
For example, the caffeine in a cup of coffee may cause extreme symptoms, such as palpitations and trembling.
Where a substance causes unpleasant symptoms, such as diarrhoea, but does not involve the immune system.
People with an intolerance to certain foods can typically eat a little quantity without having any problems.
Sheet final reviewed: 22 November 2018
Next review due: 22 November 2021
Symptoms of an allergic reaction usually develop within a few minutes of being exposed to something you’re allergic to, although occasionally they can develop gradually over a few hours.
Although allergic reactions can be a nuisance and hamper your normal activities, most are mild.
Very occasionally, a severe reaction called anaphylaxis can occur.
Getting assist for allergies
See a GP if you ponder you or your kid might own had an allergic reaction to something.
The symptoms of an allergic reaction can also be caused by other conditions.
A GP can assist determine whether it’s likely you own an allergy.
If they ponder you might own a mild allergy, they can offer advice and treatment to assist manage the condition.
If your allergy is particularly severe or it’s not clear what you’re allergic to, they may refer you to an allergy specialist for testing and advice about treatment.
Find out more about allergy testing
How to manage an allergy
In many cases, the most effective way of managing an allergy is to avoid the allergen that causes the reaction whenever possible.
For example, if you own a food allergy, you should check a food’s ingredients list for allergens before eating it.
There are also several medicines available to help control symptoms of allergic reactions, including:
- antihistamines – these can be taken when you notice the symptoms of a reaction, or before being exposed to an allergen, to stop a reaction occurring
- decongestants – tablets, capsules, nasal sprays or liquids that can be used as a short-term treatment for a blocked nose
- lotions and creams, such as moisturising creams (emollients) – these can reduce skin redness and itchiness
- steroid medicines – sprays, drops, creams, inhalers and tablets that can assist reduce redness and swelling caused by an allergic reaction
For some people with extremely severe allergies, a treatment called immunotherapy may be recommended.
This involves being exposed to the allergen in a controlled way over a number of years so your body gets used to it and does not react to it so severely.