Allergy and immunology: what the specialty covers, conditions treated and what to expect

An allergy is the immune system reacting to something that is normally harmless. The NHS lists pollen, house dust mites, foods such as peanuts, milk and eggs, animals, insect stings and certain medicines among the common triggers. Symptoms range from a runny nose and itchy eyes to hives, wheeze and, at the severe end, anaphylaxis.

Clinical immunology is the neighbouring field, and deals with the immune system being underactive, overactive against the body itself, or unusually prone to infection. In practice the two overlap in one clinic, because a person with recurrent infections, unexplained swelling or a complex reaction to a medicine may need both lenses.

The doctor in charge is usually a consultant in allergy or immunology, supported by specialist allergy nurses and dietitians. Many NHS services also have a paediatric allergy team, because children make up a large share of food allergy. Consultants reach this role through general medical or paediatric training followed by specialist training; many allergy services also draw on respiratory, dermatology and ENT colleagues.

The label matters because the management differs. Food allergy is generally managed by avoidance and an emergency plan, hay fever by medicines and sometimes immunotherapy, and hives by identifying triggers and long-term antihistamine strategies.

• Food allergy: the NHS lists cows milk, eggs, peanuts, soya, tree nuts, shellfish and wheat among the most common triggers, and notes symptoms may appear straight after eating or days later. Pollen food syndrome causes an itchy mouth after raw fruit or vegetables and is not usually serious.

• Hay fever and allergic rhinitis: seasonal or year-round sneezing, itch and blocked nose from pollen, dust mites or pets. The NHS says a GP may refer for immunotherapy if steroids and other treatments do not work.

• Anaphylaxis: a life-threatening reaction that starts within minutes of exposure; people usually stay in hospital for around 2 to 12 hours afterwards and should leave with two adrenaline auto-injectors or a prescription for them.

• Hives (urticaria) and angioedema: itchy raised rash and swelling. The NHS says that if hives does not go away with treatment you may be referred to a skin specialist.

• Insect venom allergy and drug allergy: including labels such as suspected penicillin allergy, which specialists can investigate rather than leaving a person avoiding useful antibiotics.

• Allergic asthma and atopic eczema: the NHS notes people with asthma are more likely to also have eczema, hay fever or food allergy, and that eczema can worsen with contact with allergens such as pollen, pets, dust mites and certain foods.

Good allergy testing starts with the story, not the test. The specialist asks what you ate or touched, how soon symptoms began, how long they lasted, whether treatment was needed and whether it has happened before. A positive test without a matching history does not prove allergy, which is why indiscriminate panels of tests are discouraged.

Tests that may follow include a skin prick test, where a small amount of the allergen is applied to the skin to see if it reacts; blood tests for allergen-specific antibodies; and, for food, a supervised diet in which a suspected food is removed and later reintroduced in graded amounts. Children with suspected food allergy may be assessed under specialist supervision, and some adults need a drug challenge to confirm or exclude a medicine allergy. Antihistamines can blunt skin tests, so you will be told which medicines to stop beforehand.

Component testing, a more detailed blood test that looks at individual proteins within a food or pollen, can help separate a true peanut allergy from cross-reaction with birch pollen, for example. It is used selectively and should be interpreted by an allergy specialist.

The NHS sets out four broad strategies: avoid the trigger when possible, use medicines such as antihistamines and steroid nasal sprays, tablets or creams, carry emergency adrenaline auto-injectors for severe reactions, and consider desensitisation, which should only be done by a medical professional. A specialist may also give a written allergy management plan that explains what to do if a reaction occurs.

Immunotherapy exposes the body to gradually increasing doses of the allergen over time so it reacts less. It is offered for selected people with severe hay fever, insect venom allergy and, in children with peanut allergy, the NHS notes immunotherapy may be offered while strict avoidance continues. It is slow, usually spans years and is not suitable for everyone.

Biological medicines, which block specific immune signals, are used by specialists for some difficult cases of severe asthma, chronic hives and eczema. They need specialist assessment, monitoring and, in the NHS, meeting national criteria.

In the NHS the first step is usually the GP, who may arrange initial tests or refer you to a specialist allergy clinic. In England the maximum waiting time for non-urgent consultant-led care is 18 weeks from referral, and you generally have a legal right to choose the hospital or team. Allergy services are not available in every area, so a referral may be to a neighbouring trust, and the My Planned Care website helps compare waiting times.

Privately, you can usually refer yourself or be referred by a GP. Insurers differ over whether they cover allergy testing and immunotherapy, and many ask for GP or specialist referral and a pre-authorisation code. Costs depend on the number of tests, whether a food or drug challenge is needed, and the length of any immunotherapy course, so ask for an itemised estimate. A private consultation does not replace emergency planning, and the Private Healthcare Information Network gives independent information about private providers.

Write down every reaction with the date, what you had eaten or been exposed to, how quickly symptoms began, what they were and what treatment helped. Photographs of rashes or swelling are valuable because they often fade before the appointment. Bring a list of medicines, including antihistamines, and ask the clinic in advance which to stop before skin testing. If you are bringing a child, note growth, eczema control and any foods already avoided at home.

Do not try to test yourself with a suspected trigger before the visit, and do not remove foods from a child diet without advice, since unnecessary avoidance can itself cause nutritional and social problems.

Call 999 if lips, mouth, throat or tongue swell suddenly, breathing becomes fast or difficult, the throat feels tight, skin or lips turn blue, grey or pale, or someone becomes very confused, drowsy, dizzy or faints. Use an adrenaline auto-injector straight away if one has been prescribed, lie down with legs raised, and call 999 even if the person seems to improve. If symptoms have not improved after 5 minutes the NHS advises using a second auto-injector.

See a GP if you think you or your child has an allergy, even when reactions have been mild, because the next reaction may not be.