[Zoggite]

I can't say I've ever heard about "warm vs cold" foods, but I do know that certain foods do cause mouth ulcers (aphtus): walnuts, strong cheeses, a number of fruit containing proteolytic enzymes: grapefruit, papaya, even pineapple sometimes. I don't know how, but they do.
I've also heard about yoghurt as a remedy: could it be because the lactobacillae and other microorganisms in yoghurt help restore a healthy protective microbial flora inside the mouth, therefore pushing out the bad ones? I know of gynaecologists who recommend yoghurt intra-vaginally to help treat and prevent vaginal candidiasis, thrush etc...; Similar mode of action?