Understanding Allergy: Causes, Symptoms & Treatment.
Allergy has been labelled by the World Health Organisation as a global epidemic, affecting approximately 550 million people globally. But what actually is allergy? What causes it? and how can it be treated?
We wanted to start from the very beginning, providing a baseline level of knowledge in easily digestible content that everyone can benefit from. So, let’s begin.
What is an allergy?
Mast cells and Immunoglobulin E are part of the immune response that cause allergy symptoms to be felt in the body.
Allergy is a condition where the immune system overreacts to a normally harmless substance, such as pollen, dust mites, or food. When this happens, an immune response is produced which releases chemicals, such as histamine, causing inflammation and irritation in the body.
You can be allergic to anything, and develop an allergy to anything at any time in your life. Allergies are very common, and they can cause a wide range of symptoms, including sneezing, itching, hives, swelling, and difficulty breathing.
Some people are more prone to allergies than others, and there may be a genetic component to the condition. Additionally, scientists believe that environmental factors, such as pollution and climate change, may be contributing to the increasing prevalence of allergies in recent years.
It’s important to note that allergies and intolerances are not the same thing. An intolerance is when your body simply lacks the enzyme required to break down a certain food, such as milk, which can lead to bloating, headaches, tiredness, and other unpleasant symptoms.
How are allergies diagnosed?
Skin prick tests are a common way to detect if a substance will cause an individual allergic symptoms.
If you suspect that you have allergies, your doctor will likely perform a physical exam and ask about your symptoms and medical history. They may also perform allergy testing to determine which substances are causing your symptoms. There are two main types of allergy testing:
Skin tests: During a skin test, small amounts of allergens are applied to the skin, and the skin is then pricked or scratched to see if a reaction occurs.
Blood tests: Blood tests measure the level of immunoglobulin E (IgE) antibodies in the blood, which are produced in response to allergens.
How are allergies treated?
Certain allergy medications, such as antihistamines, are taken regularly by people to help alleviate symptoms.
The best way to treat allergies is to avoid the allergens that trigger your symptoms. For example, if you are allergic to pollen, you can stay indoors during peak pollen season, use air purifiers, and keep windows and doors closed. If you are allergic to certain foods, you must avoid eating them or having contact with people who have eaten them when possible/necessary.
In addition to avoiding allergens, there are several medications that can help relieve allergy symptoms, including:
Antihistamines: Antihistamines block the effects of histamine, which can reduce itching, sneezing, and other allergy symptoms.
Nasal corticosteroids: Nasal corticosteroids reduce inflammation in the nasal passages, which can relieve congestion, sneezing, and itching.
Adrenaline pens / Adrenaline auto-injectors (AAIs): We’ll talk more about these and how they treat severe allergic reactions later on.
In severe cases, your doctor may recommend allergy shots (immunotherapy), which involve receiving regular injections of the allergen over a period of several years to desensitise your immune system.
What happens during a severe allergic reaction?
Anaphylaxis always requires an immediate emergency response.
Anaphylaxis is a severe and potentially life-threatening allergic reaction that occurs when the immune system overreacts to an allergen. An allergen is a substance that is usually harmless, but when it enters the body, it triggers an allergic reaction in sensitive individuals.
During an anaphylactic reaction, the immune system releases chemicals such as histamine and other mediators into the bloodstream, causing a rapid and severe response throughout the body.
Anaphylaxis requires immediate medical attention, as it can be fatal if left untreated. Treatment typically involves injecting epinephrine (adrenaline) into the muscle, followed by monitoring and supportive care in a hospital setting.
What can trigger a severe allergic reaction?
Common anaphylaxis triggers include:
Food
Peanuts and tree nuts are some of the most common (and potent) allergens.
You can reduce the chances of being exposed to a food allergen by:
Checking food labels and ingredients
Letting staff at a restaurant know what you're allergic to so it's not included in your meal
Remembering some types of food may contain small traces of potential allergens – for example, some sauces contain wheat and peanuts
Checking for cross-contamination in cooking supplies, oils, surface contact, etc.
Read about living with a food allergy
Insect stings
Insect stings produce venom that can cause severe allergic reactions in some people.
You can reduce your risk of being stung by an insect by taking basic precautions, such as:
Moving away from wasps, hornets or bees slowly without panicking – do not wave your arms around or swat at them.
Using an insect repellent if you spend time outdoors, particularly in the summer.
Be careful drinking out of cans when there are insects around – insects may fly or crawl inside the can and sting you in the mouth when you take a drink.
Not walking around outside with bare feet.
Some specialist allergy centres can also offer special treatment to help desensitise you to insect stings (immunotherapy).
Read more about preventing insect stings
Medicines
Some types of medicines can causes allergic reactions.
If you're allergic to certain types of medicines, there are normally alternatives that can be safely used.
For example, if you're allergic to:
Penicillin – you can normally safely take a different group of antibiotics known as macrolides.
Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin – you can normally safely take paracetamol; read the ingredients of things like cold medicines carefully to make sure they do not contain NSAIDs.
One type of general anaesthetic – others are available, or it may be possible to perform surgery using a local anaesthetic or epidural injection.
What is an adrenaline auto-injector?
The three adrenaline auto-injector brands licensed in the UK.
An adrenaline auto-injector, also known as an epinephrine auto-injector or adrenaline pen, is a medical device designed to deliver a dose of adrenaline (epinephrine) quickly and easily in emergency situations. Adrenaline is a hormone and a medication that can rapidly reverse severe allergic reactions, also known as anaphylaxis.
The auto-injector device is typically a small, handheld device that contains a pre-filled syringe with a single dose of adrenaline. It has a spring-loaded mechanism that automatically injects the medication into the thigh muscle when activated. The needle is usually hidden, and the injection process is straightforward and can be done by the person experiencing the allergic reaction or by a bystander.
It’s important to check the expiry date on adrenaline pens regularly and replace them before they expire - Most AAIs only have a shelf life of one year.
There are 3 types of auto-injector prescribed in the UK – EpiPen, Jext and Emerade – that are each slightly different.
Most adrenaline injectors come in two doses: 300mcg or 150mcg. 300mcg for treating most people over 6 years old (if they weigh more than 30kg/66lb/4.5st), whilst 150mcg doses should only be used to treat small children (who weigh less than 30kg/66lb/4.5st)
There are some adrenaline pens that come in 500mcg doses, however, studies have found that these pens are no more suited to treating anaphylaxis than a 300mcg pen (see our interview with Professor Adam Fox for more on this)
What are the symptoms of anaphylaxis?
Anaphylaxis effects the full body - airways, breathing and circulation.
Anaphylaxis is a severe allergic reaction which can be life-threatening.
Symptoms can develop suddenly and get worse very quickly.
Because the onset of anaphylaxis can be very fast, an adrenaline auto-injector should be used without delay as soon as anaphylaxis is suspected.
This should be immediately followed by dialling 999 to summon emergency medical help.
There are a number of possible signs of anaphylaxis. Any one of the following signs/symptoms is enough to warrant the immediate use of an adrenaline auto-injector:
Airway (A): swelling in the throat, tongue or upper airways (tightening of the throat, hoarse voice, difficulty swallowing)
Breathing (B): sudden onset wheezing, breathing difficulty, noisy breathing
Circulation (C): dizziness, feeling faint, sudden sleepiness, tiredness, confusion, pale clammy skin, loss of consciousness
What to do if someone has anaphylaxis:
Our full guidance on treating anaphylaxis can be found here.
Here’s a snippet from our CPD-Accredited Anaphylaxis Kitt training course for schools demonstrating how to use an adrenaline pen to treat anaphylaxis.
We provide our CPD-accredited allergy & anaphylaxis training course as part of our Anaphylaxis Kitt subscription service for schools.
