Allergies
Allergies occur when the immune system reacts to a substance that is normally harmless, such as pollen, animal dander, dust mites, certain foods or insect venoms. These substances are known as allergens.
Allergic reactions happen because the body produces immunoglobulin E (IgE) antibodies in response to a specific allergen. When exposed again, these antibodies trigger the release of chemicals such as histamine, causing symptoms.
Common allergy symptoms include:
- Sneezing, runny or blocked nose
- Itchy, red or watering eyes
- Skin rashes, hives or eczema flare-ups
- Wheezing or shortness of breath
Allergy blood tests measure levels of specific IgE antibodies to identify which allergens are triggering the immune response. Understanding your specific triggers allows for targeted avoidance strategies and appropriate management.
Causes of Allergies
Allergies develop when the immune system identifies a normally harmless substance as a threat and mounts a defensive response. This process is known as sensitisation and typically occurs over repeated exposures.
The underlying causes involve a combination of factors:
- Genetics play a significant role. Allergies tend to run in families. If one or both parents have an allergic condition (such as asthma, eczema or hay fever), their children are more likely to develop allergies
- Environmental exposure to allergens during early life can influence whether the immune system develops tolerance or reactivity. Common allergen categories include pollen, dust mites, animal dander, mould spores, insect venoms and certain foods
- The hygiene hypothesis suggests that reduced exposure to infections and microorganisms in early childhood may contribute to the immune system becoming more prone to allergic responses
Atopy is the genetic tendency to develop allergic conditions. People with atopy are more likely to produce elevated levels of IgE antibodies in response to common environmental allergens. The specific allergens that trigger a response vary from person to person and can be identified through blood testing.
Tests that can help check this condition
Learn more on the official NHS page .
