Allergy and Immunology

Allergy and immunology questions in the AKT focus on recognition, management, and emergency treatment of allergic conditions. Anaphylaxis management is the highest priority topic and questions about it appear regularly.

Anaphylaxis follows the Resuscitation Council UK guidelines. The first-line treatment is intramuscular adrenaline (1:1000, 0.5ml in adults, 0.3ml in children 6-12, 0.15ml in children under 6) given into the anterolateral thigh. This should be repeated at 5-minute intervals if there is no improvement. After adrenaline, the patient needs airway management, high-flow oxygen, IV fluid resuscitation, and observation. Tryptase levels should be taken at the time of reaction, 1-2 hours after, and at baseline (24 hours or at follow-up). Every patient who experiences anaphylaxis should be prescribed two adrenaline auto-injectors and referred to an allergy clinic.

Food allergy in children is a common presentation. IgE-mediated allergy (immediate, within minutes to 2 hours) presents with urticaria, angioedema, vomiting, and anaphylaxis. Non-IgE-mediated allergy (delayed, hours to days) presents with eczema flares, reflux, colic, and bloody stools. Cow's milk protein allergy (CMPA) is the most common food allergy in infants. NICE recommends an elimination diet followed by supervised reintroduction for diagnosis.

Drug allergy documentation is important. Penicillin allergy is over-reported, and true IgE-mediated penicillin allergy is rare (estimated at less than 10% of people labelled as allergic). De-labelling inappropriate penicillin allergy is a priority because it leads to use of broader-spectrum antibiotics and worse outcomes. AKT questions may test whether a cross-reaction is likely between specific antibiotics.

Immunodeficiency presentations in primary care include recurrent infections (more than 4 ear infections per year, 2 pneumonias, or infections requiring IV antibiotics in a normally well person). Primary immunodeficiencies include IgA deficiency (commonest, often asymptomatic), common variable immunodeficiency, and X-linked agammaglobulinaemia. Secondary causes include HIV, diabetes, malignancy, immunosuppressive drugs, and splenectomy.

Patients with asplenia or hyposplenism require lifelong prophylactic antibiotics (phenoxymethylpenicillin), pneumococcal, meningococcal, Hib, and annual influenza vaccinations. They should carry an alert card.