Recurrent meningococcal disease or unexplained lip, face, airway or abdominal swelling should prompt immune pathway thinking. Complement 5 to 9 deficiency and hereditary angioedema are different problems, but both need recognition before repeated isolated episode management.

Recurrent viral, fungal or opportunistic infection points away from simple humoral thinking. The paediatric immunodeficiency review is concise: look for congenital heart disease, cleft palate, hypocalcaemia, eczema with small platelets, ataxia, telangiectasia and live vaccine illness.

Recurrent respiratory infections with chronic diarrhoea or failure to thrive should prompt immunoglobulin thinking, not another isolated infection plan. The main distinctions are IgA deficiency, common variable immunodeficiency, X-linked agammaglobulinaemia and hyper-IgM syndrome.

A young infant with persistent diarrhoea, failure to thrive and severe infections should move severe combined immunodeficiency up the list. This is the best opener for bedside practice: ask about candidiasis, chickenpox, Pneumocystis jirovecii pneumonia and illness after live vaccination, then escalate early.

Repeated coughs and colds in childhood can still be normal, especially around nursery or school. Open this when poor growth, chronic diarrhoea, persistent thrush or severe infection makes the story less ordinary, and when targeted tests should follow the history and examination.

Sneezing, rhinorrhoea, itching and red eyes are common, and this refresher stays concrete. It helps most with separating seasonal, perennial and occupational disease from the history, then fixing trigger advice and steroid spray technique before calling treatment failure.

In infants with vomiting, diarrhoea, urticaria, wheeze or facial swelling, timing after milk exposure does the heavy lifting. The key move is separating rapid IgE-mediated reactions from delayed non-IgE disease, then matching elimination, formula choice and milk ladder use to that history.

A careful exposure history does more work here than broad allergy testing. The episode is strongest on two common mistakes: treating skin prick or serum allergen-specific IgE as proof of food allergy, and undercalling anaphylaxis when respiratory or cardiovascular features are already present.

Recurrent abdominal pain looks different when dark urine, neuropathy or blistering skin are in the history. Open this for a clear reminder that urinary porphobilinogen matters during an acute attack, while photosensitive blistering points instead towards cutaneous porphyria and sun protection.

Jaundice or anaemia after infection, broad beans, or nitrofurantoin should slow the consultation down. The useful twist is that a G6PD assay can look normal during acute haemolysis, so this is the best place to start if you want one practice-changing point today.