Hello, thanks for the query to H.C.M.C.
,foamy saliva and of course bad smell breath, off and on.
It is a case of indigestion
at first instance.
2nd and most foremost reason may be due to over feeding as I have seen this in so many cases. Fault is not with parents but due to affection and love to their spouse, parents forget that in one day a small child can not become adult.
Please don't take it otherwise as I am not blaming you as this is a common features that we forget common thing that the nature will take its course and as age passes child will become young.
When there is indigestion than there is bad smelling breath, and stomach pain, vomiting.
Pl control the diet and still there is no improvement done a blood test
and see the level of bilirubin
and also note down the level of E S R.
Is any abnormality consult a doctor. GOOD LUCK.