Allergies: An overview of causes, prevention and treatments

An allergy or hypersensitivity is an abnormal reaction by the body to a particular substance, this substance that causes the allergy is then known as an allergen. 1 in 4 people in the UK suffer from allergies…Experts have talked about the allergy epidemic as the rate of allergies and allergic reactions has increased significantly and is continuing to rise. Allergies can happen at any age, and although it is less likely to occur as you increase in age, they can still occur.

What causes allergies?

Allergies can be due to a whole host of different substances (allergens) and are usually harmless to most individuals. For people who are allergic to them, the body’s immune response goes into overdrive leading to varying levels of reactions. There are different allergens that may affect a person including:

  • Food – particularly nuts, eggs, cow’s milk and fruit
  • Grass and tree pollen – an allergy to these is classed as hay fever or allergic rhinitis
  • Medication – including ibuprofen and aspirin
  • Animal substances – flakes of dead skin or hair from cats, dogs and other animals and birds
  • Dust mites
  • Insect bites and stings
  • Latex – a material used to make gloves and condoms
  • Mould and fungus
  • Household chemicals – for example those in detergents and hair dyes

What happens in the body that leads to symptoms?

The body’s immune system is in place to defend us from dangerous foreign substances – for example bacteria and viruses. In a person who is allergic to a specific allergen, the immune system reacts in a similar way it would react to a dangerous foreign substance. In allergy, the body’s immune system overreacts to a non-harmful substance.

These are the steps that take place in the body when a person first develops an allergy:

  1. An allergen, for example pollen, enters the body through the nose and the body’s immune system recognises the pollen as foreign. For those individuals who are allergic to pollen, the body recognises this pollen as harmful, leading to an increased immune response. White blood cells, which are part of the immune system, are activated and create antibodies – these are proteins that are activated if re-exposed to pollen.
  2. When the body is exposed to pollen again, these antibodies are stimulated to activate mast cells, which are also part of the immune system which is known as sensitisation. These specific antibodies for pollen then remain on the mast cells.
  3. When the body is re-exposed again, pollen sticks to the antibodies of the mast cells. Mast cells contain antihistamine, which are released, and this further activates the immune system, which then produces the symptoms of hay-fever type allergies.
  4. Now, an allergic reaction occurs every time the body is exposed to pollen.

Possible Causes

There are different hypotheses to this, and currently there is no agreed scientific consensus.

There has been a significant increase in the number of allergies in developed countries, which has led to the ‘hygiene hypothesis’. This hypothesis suggests that rapid development of the environment and lifestyle in developed countries such as the UK does not give the human immune system enough time to adapt to the changes.

In developed countries, people are less exposed to infections during childhood, so this might put them at greater risk of developing allergies as they get older. This is because the immune system is not ‘trained’ to fight infections from an early age so it becomes sensitive to the allergens mentioned above.

Over the years, research has shown a link between certain infections and a lower chance of developing an allergy.

Other explanations for the rise in allergies may include our changing diets, and specifically the concept of the leaky gut, also known as gut permeability, leading to allergies. Vitamin deficiencies and the increase in air pollution have also been implicated in increasing allergies too.

What are the symptoms of allergies that I should look out for?

Allergic reactions usually develop within a few minutes of being exposed to an allergen. Symptoms can include:

  • Sneezing
  • Runny or blocked nose
  • Red, itchy and watery eyes
  • Wheezing and coughing


Anaphylaxis is a severe form of an allergic reaction and symptoms include:

  • Flushing of the skin
  • Hives (nettle rash) anywhere on the body
  • Swelling of throat and mouth
  • Difficulty swallowing or speaking
  • Altering heart rate
  • Nausea or vomiting
  • Sudden feeling of weakness
  • Unconsciousness

Symptoms vary depending on the type of allergy you may have. Anaphylaxis is rare but can be life-threatening, and anaphylactic shock is a severe complication of anaphylaxis. This is a medical emergency that needs to be treated immediately.

Diagnosing allergies

You do not need to see a health practitioner regarding all allergies. If you have seasonal allergies (hay fever) – for example to pollens which cause rhinitis symptoms, then these can be usually managed by with medications from a pharmacy or online from Some medications such as fexofenadine are prescription only so require a doctor’s approval such as fexofenadine. Fexofenadine is often seen as the medication of choice when others bought from the pharmacy do not work. TheDoctorService can provide fexofenadine on prescription at

Some allergies are managed mainly by avoidance, for example with cat and dog allergies. Discussing your symptoms with a health practitioner may be useful in getting further advice to control your symptoms. If it’s not obvious what your allergy is, or you have had an anaphylactic (severe) reaction then you should seek advice from a specialist or your GP to consider further testing.

The tests may include:

  • Skin prick testing – putting a drop of the suspected allergen into your forearm to see if you develop an allergic reaction to it
  • Blood tests – a sample of blood is taken and analysed to see whether you have specific antibodies in response to an allergen
  • Patch tests – used to diagnose a specific type of eczema – small amount of suspected allergen is added to special metal discs which are taped to your skin and monitored for a reaction

Preventing Allergies

Complete avoidance of the allergen would be the best way to prevent an allergic reaction – but this isn’t always practical. Here are some ways you can minimise exposure to the most common allergens:

  • Carefully check the list of ingredients on food packaging
  • In a restaurant, do not rely on the menu description alone and communicate with waiting staff about specific allergens
  • Avoid places where different foods come into contact with each other e.g. bakeries and buffets
  • Always check what allergens are in a dish even if you have eaten it before
Animal substances

If you have an allergy to pets, we recommend as far as possible complete avoidance. If you are unable to do this then we suggest:

  • Keeping pets outside as much as possible
  • Wash pets at least once a week
  • Regularly wash soft furnishings on which pets lay
  • Increase ventilation in rooms where pets reside
Dust mites
  • Replacing carpet with wooden floors
  • Fitting roller blinds that can easily be cleaned
  • Using a vacuum cleaner fitted with a HEPA filter
  • Regularly wiping surfaces with a damp, dry cloth

Allergy treatments

Minor allergic reactions are often treated by over-the-counter remedies and medication, which can be purchased without a prescription at These include antihistamines such as: cetirizine or loratadine.


Antihistamines reduce the histamine your body produces during an allergic reaction from causing allergic symptoms. They can be used to prevent an allergic reaction or can be taken as and when you begin to feel the symptoms. Always ask your pharmacist or GP for advice about suitability before starting a new medication.

More specific allergies, for example hay fever might require other specific treatments. These have been covered in more detail in a separate article, but this is a brief summary

  • Antihistamine tablets and syrups
  • Antihistamine nasal sprays
  • Nasal corticosteroids – to reduce inflammation in nasal passages
  • Antihistamine eye drops – for itchy, red, watery eyes
Other treatments
  • Decongestants – short-term treatment for a blocked nose caused by an allergic reaction
  • Lotions and creams – to treat red and itchy skin
  • Steroid medication – reduce inflammation caused by allergic reaction –inhalers for asthma, creams for eczema and nasal sprays can all contain steroids.
  • Severe reactions may need oral steroids and emergency adrenaline too if it is a life threatening emergency.

For individuals with severe and persistent allergies who are not able to control their symptoms, desensitisation may be an option. This involves giving the individual immunotherapy injections or tablets containing small doses of the allergen at regular intervals over the course of several years. The aim is to allow your body to get used to the allergen so that over time, it doesn’t produce such a severe allergic reaction. This will not necessarily cure your allergy but may mean you have to take less medication in the future. This form of treatment is usually managed by an allergy specialist.


We hope you’ve got a clearer picture of allergies, the causes and ways to prevent them. If you would like further advice or would like treatment for Fexofenadine, please visit and for other over the counter remedies please visit

Edited by Dr Kiran Sodha & The Doctor Service

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