Allergy and Immunology

Allergy happens when the immune system reacts to a substance that is normally harmless, such as pollen, house dust mite, a food, a medicine or an insect sting. Symptoms range from sneezing, itchy eyes and rashes to wheezing, swelling of the lips and throat and, less often, anaphylaxis, a sudden and potentially life-threatening reaction affecting breathing and circulation. Immunology deals with the immune system more broadly, including immune deficiencies, in which the body cannot fight infection properly, and some conditions in which the immune system causes swelling or inflammation. Allergists and clinical immunologists work out what is triggering symptoms, how serious the risk is and how to reduce it. Their work combines a careful history, targeted testing and treatment that ranges from avoidance advice and medicines to immunotherapy that gradually retrains the immune system. Care for children and adults often runs side by side, as many allergies begin in childhood.

The most common conditions are allergic rhinitis and conjunctivitis (hay fever), allergic asthma and atopic eczema, which often occur together. Food allergy, for example to peanut, tree nuts, milk, egg, fish, shellfish or sesame, can cause reactions within minutes and needs a clear diagnosis and plan. Drug allergy is another large area: many people carry a penicillin or anaesthetic allergy label that, when tested, turns out not to be a true allergy, and removing it widens safe treatment options. Insect venom allergy to bee or wasp stings can be serious and responds well to treatment. Chronic urticaria (hives lasting more than six weeks) and angioedema, including the inherited form called hereditary angioedema, are also managed here. On the immunology side, primary immunodeficiencies, often suspected because of frequent, severe or unusual infections, are diagnosed and treated, sometimes with lifelong antibody replacement.

Treatment begins with knowing exactly what to avoid and how. For hay fever and allergic asthma, nasal sprays, antihistamines and inhalers control most symptoms. Allergen immunotherapy, given as regular injections under the skin or as daily tablets or drops under the tongue, gradually reduces sensitivity to pollen, dust mite or insect venom and is usually continued for about three to five years. For people with food allergy, a personal plan covers avoidance, reading labels and what to do if a reaction happens, and some children may be suitable for supervised oral immunotherapy. Anyone at risk of anaphylaxis is prescribed adrenaline auto-injectors and trained in their use. Severe asthma, chronic hives and some types of eczema may be treated with biologic medicines that block specific steps in allergic inflammation. People with antibody deficiency may receive regular immunoglobulin replacement by drip or by injection under the skin.

Testing is chosen to answer the question raised by your history. Skin prick tests place a tiny drop of allergen on the forearm and lightly prick the skin, with results visible in about 15 to 20 minutes. Intradermal tests inject a small amount into the skin and are used mainly for medicine and venom allergy. Patch tests, worn on the back for about 48 hours, look for delayed contact allergy to metals, fragrances or preservatives. Blood tests measure specific IgE antibodies to allergens, and component testing can show which protein in a food is responsible, which helps estimate how severe a reaction might be. When the answer is still uncertain, a supervised oral food challenge or a drug provocation test is the reference test that settles the question. Lung function testing assesses asthma, and immune blood tests measure antibody levels and vaccine responses when an immune deficiency is suspected.

Before travelling, send a summary of your reactions, including what you ate or took, how quickly symptoms began and how they were treated, plus any previous test results. Ask your coordinator which medicines to stop before testing: antihistamines usually need to be stopped about five to seven days beforehand, and some other medicines may also affect results, but never stop asthma or heart medicines without advice. Most allergy assessments are outpatient and take one to three days, with a challenge test taking a full day under observation. Immunotherapy and immunoglobulin treatment are long-term, so plan how they will continue after you leave: under-the-tongue treatment can be taken at home, while injections need a local clinic. If you carry an adrenaline auto-injector, keep it in your hand luggage with a doctor's letter. Interpreter and international patient support is commonly available.