Allergies: What they are and how we treat them

What is an allergy?

An allergy is a sensitivity to a particular substance. These substances, known as allergens, commonly include; foods, medication, animal dander, pollen, dust and chemicals. During an allergic reaction, the body’s immune system responds adversely and overreacts to an allergen, which would normally be harmless to most people.

An allergic reaction can cause a wide variety of symptoms, which can range in severity from very mild to life-threatening. Symptoms of an allergy can include; rash, itch, tingling, nasal irritation, sneezing, swelling, breathing difficulties, nausea & vomiting, upper abdominal pain, difficulty swallowing, feeling lightheaded or dizzy.

Why do people get Allergies?

Unfortunately, our understanding of why people develop allergies and how these allergies can change throughout life is not complete. However, there are some known risk factors. Allergies can run in families indicating there is a strong genetic component for some people. They are also more common in individuals who suffer from other allergy-related conditions such as; asthma, eczema & hayfever. It is apparent that allergies are becoming more common, particularly for people growing up in cities and the industrialized world. Whilst there are various theories as to why this is, the exact reason remains subject to debate.

Food Allergies

The most common food allergies encountered are to; milk, eggs, soya, nuts, fish, shellfish & fruit. Food allergies in childhood are common and whilst many people will outgrow them, for others they may persist. New food allergies can develop in adults who have never had allergies previously and the severity of these allergies can change.


Asthma is a condition where the airways in the lung become inflamed. This restricts airflow causing breathing difficulty. There are many different triggers to asthma that vary from person to person and there can be multiple triggers for an individual. It is important for asthma sufferers to be aware of possible allergic triggers, with common culprits being dust, pollen & animal dander.


Hayfever is a seasonal allergy to pollen. It is very common and can affect up to 1 in 5 people at some point in their lives. There are many different types of pollen including tree pollens, grass pollens & weed pollen. Common symptoms include; sneezing, nasal irritation, eye irritation, itching of the throat, cough & fatigue.

Identifying Allergens & Allergy Testing

Sometimes identifying an allergen can be straightforward through simple self-identification from a person’s experiences or discussion with a medical professional. In other cases where triggers aren’t clear, or there is a suggestion of more severe allergies where caution is needed, allergy testing can play a useful role.

There are different types of allergy tests.  It is important that allergy testing is organized by someone with the appropriate expertise as whilst they can be useful, interpretation of results can be complicated and need correlated to a patient’s symptoms. Sometimes allergies can be suggested that are not in fact present, and equally, allergies can be missed. The wide variety of possible allergens also adds to the complexity & practicalities of testing.

Skin prick testing is where the skin is pricked with a tiny amount of the suspected allergen and then observed for a short period of time to see whether a reaction is evident. This is generally a safe & often useful form of testing which is typically done within a specialist setting.

Blood tests for allergies can be done alongside or sometimes instead of skin prick testing. When someone into contact with an allergen, the body produces a substance called an antibody. Testing for the presence of these specific allergy related antibodies can sometimes help in the diagnosis of allergies or be useful in suggesting possible allergies.

Patch testing for allergies can be useful when patients have skin symptoms that may be caused by their skin coming into direct contact with an allergen. This form of testing involves small discs containing potential allergens being taped to the back with follow up appointments to observe for any consequent skin reactions. This is usually done within dermatology clinics.

How Can London Doctors Clinic Help?

Our experienced General Practitioners based across our convenient, easily accessible locations with same day appointment availability are here to assist. We can discuss your concerns with you in a friendly empathetic manner, help diagnose allergies, advise you with regards to medical management of allergies and direct you towards further tests or specialist referral if appropriate.


Book Now


Article written by Dr Seth Rankin, General Practitioner and Chief Medical Officer at London Doctors Clinic 

Published: November 2018

Review date: February 2023