Usually just a marker of atopy, so common with asthma, hay fever, eczema.

But beware rare things eg HyperIgE syndrome. Also seen with malignancy, PFAPA, Familial Mediterranean Fever. With the rheumatological conditions, eosinophilia is often severe (>5) but with malignancy, usually mild… [Turkish study and protocol, not v useful European Journal of Pediatrics volume 182, pages2833–2842 (2023)]

And helminth infection, viz

  • Fever and hepatosplenomegaly
  • Liver/lung/brain cysts
  • Uveitis/macular oedema
  • Anaemia with abdominal pain or wheeze