Allergies

What is an allergy?

An allergy is a reaction the body has to a particular substance — called an allergen — that is normally harmless to most people. In someone with an allergy, the immune system mistakenly identifies the allergen as a threat and mounts a response against it, releasing chemicals such as histamine that cause the symptoms of an allergic reaction. Common allergens include pollen, dust mites, animal dander, certain foods, insect stings and some medicines.

Allergies are very common and can develop at any age, though they often begin in childhood. They tend to run in families, and someone with one allergic condition may be more likely to have others. Most allergic reactions are mild and more of a nuisance than a danger, causing symptoms like sneezing, itching or a rash. Rarely, however, an allergy can cause a severe, life-threatening reaction called anaphylaxis, which is why understanding allergies and knowing the warning signs matters.

Common allergens and triggers

Allergies can be triggered by a wide range of substances, and people are often allergic to specific ones rather than allergens in general. Identifying your triggers is central to managing an allergy. Common allergens include:

• •Pollen from grass, trees and weeds (causing hay fever)
• •House dust mites
• •Animal dander (skin flakes), such as from cats and dogs
• •Foods such as nuts, shellfish, eggs, milk and others
• •Insect stings, such as from bees and wasps
• •Certain medicines
• •Latex and some other substances

Symptoms

Allergy symptoms depend on the allergen and how the body is exposed to it, and can affect the nose, eyes, skin, airways or digestive system. Most are mild to moderate. Common symptoms include:

• •Sneezing, and a runny or blocked nose
• •Itchy, red or watering eyes
• •Wheezing, coughing or shortness of breath
• •An itchy rash or hives, or raised, itchy skin
• •Swelling of the lips, tongue, eyes or face
• •Tummy pain, feeling sick, vomiting or diarrhoea (with food allergies)

Treatment and management

The most important part of managing an allergy is, where possible, avoiding the allergen that triggers it — for example, avoiding a particular food, reducing exposure to dust mites, or staying indoors when pollen counts are high. Since complete avoidance is not always possible, treatments help control symptoms. Antihistamines, available as tablets, nasal sprays and eye drops, reduce the sneezing, itching and other symptoms of many allergies and are widely used.

For nasal symptoms, steroid nasal sprays help, and for skin reactions, soothing creams or antihistamines ease itching. A pharmacist can advise on suitable treatments for milder allergies. For more troublesome or complex allergies, a doctor can help identify triggers through allergy testing, advise on management, and in some cases offer treatments that gradually reduce sensitivity to a specific allergen. People with severe allergies may be prescribed emergency medication to carry with them.

Severe allergic reactions (anaphylaxis)

While most allergic reactions are mild, it is essential to be aware of anaphylaxis — a severe, potentially life-threatening allergic reaction that requires immediate emergency treatment. Anaphylaxis usually develops rapidly after exposure to the allergen (such as a food, insect sting or medicine to which someone is severely allergic) and affects the whole body.

Warning signs of anaphylaxis include difficulty breathing or noisy breathing, swelling of the tongue, throat or mouth, a tight throat or difficulty swallowing, a widespread rash, feeling faint, dizzy or collapsing, and a sense of impending doom. Anaphylaxis is a medical emergency — emergency help should be called immediately. People known to be at risk are usually prescribed an adrenaline auto-injector to use in an emergency, and should use it without delay if anaphylaxis is suspected, then seek emergency care.

For the vast majority of people with allergies, reactions are mild and anaphylaxis is not a concern. But because it can be so serious, anyone who has had a severe reaction, or who has a known severe allergy, should be assessed by a doctor, carry any prescribed emergency medication, and know how and when to use it. Understanding the difference between a mild reaction and the warning signs of anaphylaxis allows a calm, appropriate response to each.