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What is an allergy?

Andrew Bellingham

Andrew Bellingham

Pharmacist | 20+ Years | BPharm | Dip Clin Pharm

An allergy occurs when the body’s immune system overreacts to substances it perceives as harmful, known as allergens. This response involves the production of antibodies called immunoglobulin E (IgE), which trigger the release of chemicals like histamine upon re-exposure to the allergen.

Most common allergies

Many things can make some people’s bodies react in an allergic way, the most common are: 

  • Hay fever: Pollen from trees, grasses, and weeds
  • Dust mites: tiny insects found in dust
  • Pets: skin cells, saliva, and urine of pets like cats and dogs
  • Mould: spores that grow in warm, damp conditions
  • Food: nuts, shellfish, eggs and milk
  • Insect stings: bees, wasps and ants
  • Medicines: certain antibiotics, painkillers or chemotherapy drugs

What is the rarest allergy?

While most allergies are well-known reactions to common substances like pollen or pet dander, there’s a spectrum of rare allergies that you may not have heard of before.

These include:

  • Water allergy (aquagenic urticaria): hives or welts when in contact with water

  • Sunlight allergy (solar urticaria): itching or hives upon exposure to sunlight

  • Exercise-induced anaphylaxis: severe allergic reaction to physical activity, including hives and difficulty breathing

  • Cold urticaria: hives, itching, or swelling due to cold temperatures

  • Meat allergy (alpha-gal syndrome): carbohydrates in red meat can cause hives, stomach cramps, and potentially severe symptoms

Symptoms of an allergic reaction

Allergic reactions can vary in severity, ranging from mild discomfort to life-threatening emergencies. It’s crucial you recognise the symptoms and know when to seek medical help. 

Mild allergy symptoms:

  • Itchy or watery eyes
  • Runny or stuffy nose
  • Sneezing
  • Mild skin rash or hives
  • Mild itching or tingling sensation in the mouth

Severe allergy symptoms (anaphylaxis):

  • Difficulty breathing or shortness of breath
  • Tightness in the chest
  • Rapid or weak pulse
  • Severe swelling, particularly of the throat or tongue
  • Dizziness or lightheadedness
  • Loss of consciousness

When to seek medical help:

Call 111: For moderate symptoms that are causing distress but are not immediately life-threatening.

Call 999: For severe symptoms, especially if they involve difficulty breathing, swelling of the throat, or loss of consciousness. Anaphylaxis requires immediate medical attention and administration of epinephrine.

Frequently asked questions about allergies

What are allergy symptoms and triggers?

Allergy symptoms include sneezing, itching, and rashes. Common triggers are pollen, dust, and certain foods.

Can allergies develop later in life?

Yes, allergies can develop at any age due to exposure to new allergens or changes in the immune system.

How are allergies diagnosed and treated?

Allergies are diagnosed through skin tests or blood tests. Treatment involves avoiding allergens, medications like antihistamines, or allergen immunotherapy.

A woman with hay fever sneezes into a tissue while stood in front of a tree with pink blossom

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The conditions covered by Pharmacy First are:

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