I think Tinkers might be right...she might be more prone to these sort of things as I presume her brother eats the same food,plays out etc?
She doesn't have any underlying problems? Has she had a few courses of antibiotics over a short period of time? Could be worthwhile starting her on some probiotics, any imbalance in her healthy bacteria could have weakened her immune system.
Yup, DS eats the same food (which is pretty healthy). She walks to school (but it's only 150 yds!), plays out at break etc. I'm not a clean freak and we have cats, so there must be a fair exposure to dirt.
No underlying health problems, last antibiotics probably last year (she tends to get an ear infection about once a year and had gromits at 4), but only one course at a time.
Thinking about the gromits reminds me that she had her tonsils taken out at the same time - they were absolutely massive and the surgeon said they would be bound to have to come out later. But I do remember hearing that tonsils are a first line of defence against infection so, if they work, they are worth keeping. Perhaps that is the difference, as DS still has his!
I will try vitamins and probiotics again - have tried from time to time, but it's hard to find one with an acceptable taste!