Allergies: An Overview

Everything you need to know about allergies, including what causes them and how to treat or prevent allergic reactions.

What is an allergy?

Allergies are the negative reactions bodies have to particular foods or substances. They are very common, affecting as many as one in four people in the UK at some point in their lives according to the NHS.

Everyone responds to reactions differently, with symptoms ranging from mild to severe. The causes of allergies are fairly consistent between people, however, with dust, grass, pollen and certain foods being frequently reported as allergens.

Allergies are particularly common in children, and although some allergies disappear as a child gets older, most allergies are lifelong affairs – with some adults developing all new allergies along the way too.

Frustrating though some allergies may be to accommodate, allergic reactions are generally easily avoided with enough communication between the allergy sufferer and friends, family and co-workers. Further for the most part, allergic reactions are mild – though obviously exceptions do exist and severe reactions can undoubtedly occur.

What causes an allergic reaction?

Allergic reactions occur when the immune system treats a substance as harmful, producing antibodies that target the non-harmful allergen. This reaction can inflame the skin, sinuses, airways or digestive system to varying degrees – producing minor rashes and irritation to some, fully fledged anaphylaxis to others. The latter is a life-threatening emergency, the former is not.

What are the most common allergies?

The most common allergens, according to the NHS, are as follows:

  • Grass and tree pollen (hay fever)
  • Dust mites
  • Animal dander (skin or hair)
  • Nuts, fruit, shellfish, eggs and cows' milk
  • Insect bites and stings
  • Ibuprofen, aspirin and certain antibiotics
  • Latex
  • Mould
  • Household chemicals

What causes an allergy?

Research has not made it clear why allergies develop in people. All we know right now is that most people affected by allergies have a family history of allergies or conditions like asthma or eczema.

Research is even less clear as to why the number of reported allergies is increasing year on year. The prevailing theory (sometimes referred to as the 'hygiene hypothesis') is that because we are living in cleaner environments than we have in the past, and have the tools at our disposal to keep them that way, we are less frequently exposed to infections and microorganisms.

The infections that we are protecting ourselves from with extreme cleanliness are usually instrumental in promoting the normal development of immune responses. When exposure to them is reduced, without also reducing exposure to otherwise harmless environmental allergens, there is a tendency for people to develop inappropriate immune responses to common, typically harmless environmental allergens – and so an allergy is born.

What forms of allergic reaction are there?

Some of the most frequently occurring allergic reactions in the UK today.

Enter a condition or symptom to filter the conditions below.

What are the common signs of an allergic reaction?

The symptoms you may or may not observe depend on the substance that triggered them. As such, there are different groups of common signs to look out for depending on the allergen:

An allergic reaction to pollen might cause:

  • Sneezing
  • Itchy eyes, nose or roof of mouth
  • A stuffed or runny nose
  • Watery, red or swollen eyes

An allergic reaction to food might cause:

  • Swelling of the lips, tongue, face or throat
  • Tingling in the mouth
  • Hives
  • Anaphylaxis

An allergic reaction to an insect sting or bite might cause:

  • Swelling at the site of the sting
  • Itching or hives throughout the body
  • Coughing, chest tightness or shortness of breath
  • Anaphylaxis

An allergic reaction to a specific medicine might cause:

  • Facial swelling
  • Itching or hives throughout the body
  • Coughing, chest tightness or shortness of breath
  • Anaphylaxis

When is an allergy an intolerance?

An allergy is an immune response to a traditionally harmless substance. An intolerance produces unpleasant symptoms, for example diarrhoea, but does not involve the immune system.

Both allergies and intolerances are differentiated from sensitivities, which provoke exaggerated, but not extreme effects to a substance. A caffeine sensitivity, for example, might produce trembling or heart palpitations.

Your allergy questions, answered

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How are allergies diagnosed?

Allergies are diagnosed in three main stages:

  • Asking questions about signs, symptoms and family history
  • Performing a physical exam
  • Keeping a diary of symptoms and potential triggers

The diagnosis of suspected food allergies involves two additional steps:

  • Keeping a diary of foods eaten during the week
  • Identifying and stopping eating a suspected allergen food, then reporting back

There are two more diagnostic routes that the doctor may choose to pursue:

  • Skin tests, wherein a doctor or nurse pricks the skin and exposes you to small amounts of potential allergens to see if they can get a controlled, small scale reaction
  • Blood tests, where the amount of allergy-causing antibodies in your bloodstream is measured

How are allergies treated?

The first line of treatment with regard to allergies is simply avoidance, i.e. taking steps to identify your allergy triggers, and then adjusting your diet, environment and so on to accommodate them. Communication with family, friends and co-workers will make this process much easier.

That said, there are multiple treatment options available to you. Medication can reduce the immune system response and ease your symptoms, be it with prescription medication or over-the-counter nasal sprays or eyedrops. More severe allergies may require immunotherapy administered by injection or a sustained course of medication.

How can prevent an allergic reaction?

The best way to prevent an allergic reaction is to avoid the substance that you are allergic to altogether. Advice for any major allergy is widely available online. As you might expect, the NHS website is a good starting point in this regard.

Those at risk of severe allergic reactions like anaphylaxis should carry at least two adrenaline auto-injectors at all times. Make friends, family and colleagues aware of your allergy so that they can administer your adrenaline injections if the worst happens. For when you are alone and in public, consider wearing a MedicAlert or Medi-Tag medallion or bracelet to make strangers aware of the severity of your allergy at just the right moment.

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