Thank you for your question.
Body odour is a very subjective thing. Generally this is genetically determined. There has been some research to show that if you find an opposite sex's BO unbearable, it usually means that he/she is very genetically similar to you. The conduct of the study is very very interesting, if not gross.
It is usually not a sign of illness. There are some caveats though, where some patients with liver or kidney disease start to have a smell that is beyond the normal body odour. This sign can usually only be detected by experienced doctors or nurses, since there is no official laboratory test for smell.
But well, if you are worried, you should pop by your usual GP to have a "smell test", if not a simple blood test to screen for these disorders.
