Allergies - Definitive Guide

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What is an allergy?

An allergy occurs when your immune system reacts to a normally harmless substance, triggering a process in your body called an allergic reaction. The substances that trigger an allergic reaction are called allergens

Common allergens include: 

  • pollen —in particular tree or grass pollen. These cause symptoms of hay fever including sneezing, and itchy, watery eyes. 
  • food —in particular foods like peanuts, eggs, milk, and shellfish. Foods may cause gastric symptoms like nausea, vomiting, and diarrhoea, or may lead to a serious allergic reaction called anaphylaxis. 
  • animal dander —tiny flakes of skin from pets like dogs and cats can trigger symptoms like sneezing, runny nose, and itchy, watery eyes
  • household chemicals —such as cleaning products can trigger symptoms of asthma such as wheezing, or cause skin irritation or a rash
  • house dust mites —are tiny pests that live in dust and household objects like pillows, carpets, mattresses, and upholstery. They trigger symptoms similar to pet dander allergy. 
  • mould —are tiny fungi that release spores into the air. They may trigger asthma symptoms, cough, and itching of the eyes, nose, and throat. 
  • medicines —in particular antibiotics, anticonvulsants, and non-steroidal anti-inflammatory drugs (NSAIDs). Symptoms of drug allergies include rash, shortness of breath, swelling, and in some cases, a severe reaction called anaphylaxis (where the eyes, lips and airways swell, which stops breathing and can cause death if not treated). 
  • latex —such as in latex gloves or some types of condoms. A latex allergy can cause itchy, watery eyes, difficulty breathing, runny nose, and cough. 
  • insect bites and stings —including bee and wasp stings and mosquito bites. Some stings and bites cause local irritation, redness, pain, and swelling of the skin, while others, particularly bee stings can cause anaphylaxis. 

How serious is an allergic reaction?

Allergic reactions range from being a minor annoyance to severe and even life-threatening. 

Common symptoms may include: 

  • sneezing
  • runny nose
  • itchy eyes
  • pain or tenderness around the eyes, cheeks, and forehead
  • coughing
  • itchy rash

Sometimes an allergic reaction can be serious and life-threatening. This is known as anaphylaxis and is a medical emergency. 

Symptoms of a severe allergic reaction (anaphylaxis) include: 

  • swelling of the eyelids, lips, face, and tongue
  • difficulty breathing or talking
  • wheezing (noisy breathing)
  • tightness in the chest and throat
  • raised, itchy rash (hives) 
  • swelling, blistering, or peeling of the skin 
  • nausea and vomiting
  • feeling dizzy or weak
  • collapse

Anaphylaxis is a medical emergency. If you, or someone you know experiences symptoms of anaphylaxis, call an ambulance immediately.

What’s the difference between food allergies, food intolerance, and food sensitivity?

A food allergy is when your immune system overreacts to a perceived threat, in this case, food. Severe food allergies can trigger anaphylaxis which may be life-threatening. People with food allergies often have to carry an injection of epinephrine called an EpiPen in case they unknowingly come into contact with the food they are allergic to. 

Food intolerance normally relates to difficulty digesting certain foods. Lactose, a kind of sugar found in dairy products is a common intolerance. Symptoms of food intolerance include abdominal pain, bloating, and diarrhoea. 

Food sensitivity is a poorly understood condition where eating certain foods appears to trigger symptoms like rashes, stomach pain, joint pain, fatigue, and brain fog. Gluten appears to be a common cause of food sensitivity.  

Why do people have allergies?

Normally, our immune systems defend us against threats like viruses, bacteria, and harmful substances such as toxins. One of the ways our immune system defends us is by producing a chemical called histamine

When we have an allergy, our body produces histamine in response to a substance that is not dangerous such as pollen, animal dander, or certain foods. 

The release of histamine triggers inflammation of the skin, digestive system, sinuses, or the airways of the lungs causing symptoms of an allergic reaction. 

What causes allergies is not fully understood, but they tend to run in families. Some types of allergies like food allergies are becoming more common though it isn’t clear why this is the case.

How to get rid of allergies

There are several long and short-term treatments for allergies. Some focus on treating allergy symptoms when they occur, some on preventing allergy symptoms, and some on stopping your body from reacting to the allergen in the first place. 

The best treatment for you depends on the type of allergy you have and how severe your symptoms are. Talk to a doctor about the best way to manage your allergy. 

Treatments for allergies include: 

  • avoiding contact with the substance you are allergic to —this is often the safest and most effective way to treat allergies, though it may not always be possible or practical
  • taking over the counter medications like antihistamines, eyedrops, nasal sprays, or steroid creams to prevent or treat your allergy
  • if you have a severe allergy that may lead to anaphylaxis, you may be given an adrenaline (epinephrine) injector pen called an EpiPen to use in emergencies. Always carry your EpiPen with you, and check it regularly to make sure it’s in date. 
  • Immunotherapy or desensitisation therapy involves being gradually exposed to an allergen over a long period of time until your body becomes desensitised and doesn’t react as severely. 

The allergen can be given by injections, drops under the tongue (sublingual immunotherapy), or controlled amounts of the food you are allergic to (oral immunotherapy). Talk to your GP about immunotherapy. 

Children often outgrow their allergies as they get older. 

Get help from an online doctor

An online doctor can help with allergies by asking about your symptoms, helping you to identify what is triggering your allergy, and recommending or prescribing medications to treat your symptoms. They can also recommend some things you can do to reduce your allergy symptoms and suggest further investigations and treatments if needed. 

It’s easy to book an appointment with an NHS-trained GP at Medicspot. Simply click the link and select an appointment at a time and day that suits you. Appointments are often available the same day. 

Get help from a pharmacist

A pharmacist can help with allergies by recommending over-the-counter medications like antihistamines, eyedrops, nasal sprays, or topical creams to help relieve your symptoms. A pharmacist can also advise you on when you need to see a GP. 

Find a pharmacy near you 


Allergies are an increasingly common condition with a variety of causes. While most allergies are mild and can be managed by avoiding contact with the allergen or over-the-counter medications, some allergies can significantly impact your quality of life and may even be life-threatening. 

If you or your child have symptoms of allergies and would like to talk to a doctor, make an appointment today. 


NHS: Allergies  August 2nd 2022 (Accessed November 25th 2022) 

Mayo Clinic: Allergies  August 5th 2022 (Accessed November 25th 2022)

American Academy of Allergy, Asthma, and Immunology: Allergic Reactions  September 28th 2020 (Accessed November 25th 2022)

PubMed: Food Allergy April 2018 (Accessed November 25th 2022)

Harvard Health Publishing: Food allergy, intolerance, or sensitivity: What’s the difference, and why does it matter? January 30th 2020 (Accessed November 25th 2022)

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