Woman outside in a field blowing nose, allergies


Understanding Allergies: All You Need to Know

Understanding Allergies

What is an allergy?

An allergy is a reaction the body has to a particular food or substance.1

What causes allergies?

Allergies occur when the body’s immune system reacts to a usually harmless substance as though it’s harmful. Allergies are very common and the number of people living with allergies is on the rise. In the UK 1 in 4 people are affected by an allergy at some point in their lifetime.1

Most people affected have a history of allergies in their family or have a related condition such as asthma or eczema.1

Allergies are particularly common in children, some disappear as the child gets older, although many are lifelong. Adults can develop allergies to things they were not previously allergic to.1

Types of Allergies

How many types of allergies are there?

Substances that cause allergic reactions are called allergens and there are several types of allergen including:1

  • Grass and tree pollen, the allergen that causes hay fever (allergic rhinitis)
  • Dust mites
  • Animal dander - tiny flakes of skin and hair
  • Food - e.g. nuts, shellfish, fruit, eggs, and cow’s milk
  • Insect bites and stings
  • Medicines – e.g. ibuprofen, aspirin, and certain antibiotics  
  • Latex
  • Mould – small particles released into the air that you can breathe in
  • Household chemicals - e.g. detergents and hair dyes

Allergy Symptoms

How will I know if I’m having an allergic reaction?

Allergic reactions usually happen within a few minutes of exposure to an allergen. Symptoms of an allergic reaction include:1

  • Sneezing
  • A runny or blocked nose
  • Red, itchy, or watery eyes
  • Wheezing and coughing
  • A red, itchy rash
  • Worsening of asthma or eczema symptoms

Allergy Treatments

How do I treat allergies?

The treatment for allergies will depend on what you’re allergic to. A variety of medicines which can treat mild allergies are available from pharmacies without a prescription. However, you should always ask your GP or pharmacist for advice before starting new medication.3


Antihistamines are the main course of treatment for allergies, including allergy sinusitis symptoms. They block the effects of histamine in your body. Histamine is normally released when the body detects something harmful such as an infection. However, in people with allergies, the body mistakes something harmless for a threat and produces histamine. It’s the histamine that causes the unpleasant symptoms of an allergic reaction.2

Antihistamines help prevent this process if you take them before coming into contact with allergens, or they can reduce the severity of your symptoms if taken afterwards.2

They can be taken as tablets, capsules, creams, liquids, eye-drops, or nasal sprays, depending on which part of the body is affected.3


Decongestants can be used as short-term treatment for a blocked nose caused by an allergic reaction such as an allergy sinus infection. They work by reducing the swelling of blood vessels in the nose, which helps to open the airways.3

Decongestants can be taken as liquids, tablets, capsules, or nasal sprays, however, they should not be used over an extended period of time as they can make the symptoms worse.3

Lotions and Creams

If you have an allergic reaction on your skin, this can be treated with over-the-counter creams and lotions such as:3

  • Moisturising creams to keep the skin moist and protect it from allergens
  • Calamine lotion to reduce itchiness
  • Steroids to reduce inflammation


Steroid medications can help reduce inflammation caused by an allergic reaction.3

They’re available as:3

  • Nasal sprays and eye drops for an inflamed nose and eyes
  • Creams for eczema and contact dermatitis
  • Inhalers for asthma
  • Tablets for hives (urticaria)

Sprays, drops and weak steroid creams are available without a prescription.3


If other allergy treatments don’t work, your GP might refer you for immunotherapy. This involves small amounts of the allergen being introduced to slowly build up immunity, either as an injection, or as drops or tablets under the tongue. This treatment does not cure the allergy but will make it milder so you can take less medication.3

It’s important to know that immunotherapy is a specialist treatment and may not be available everywhere.1


  1. Allergies. NHS. https://www.nhs.uk/conditions/allergies/ Accessed 27/01/2022.
  2. Antihistamines. NHS. https://www.nhs.uk/conditions/antihistamines/ Accessed 27/01/2022.
  3. Allergies Treatment. NHS. https://www.nhs.uk/conditions/allergies/treatment/ Accessed 27/01/2022.