It is expected that the small quantities of fluorides put into toothpaste can fluoridate the fatty acids present in almost all mammalian nipples, causing minute quantities of hydrofluoric acid to be released into the bloodstream. Normally HF is very toxic and bad for bones since it displaces calcium, but it is well established that low levels of HF over extended periods has proven to suppress nerve activity - hence the danger of HF acid burns since they are initially painless. This nerve suppression is believed to affect the brain, even in low concentrations, to produce a mild euphoria.