One reader's seven-year-old son is developing yellow spots on his teeth. According to ayurvedic medicine, one reader tells us, it's caused by a pitta imbalance, which, in Western terms, means he's probably acidic. It's probably more of a mineral imbalance, says another reader who suggests seeing a celloid mineral therapist. Fluorosis, from fluoridated water and standard toothpastes, could be another possibility, so filter your water and buy non-fluoridated toothpaste, which is available in health stores. Another reader recalls her son having the same problem, which the family doctor described as 'tetracycline teeth', caused by the antibiotic. Its effects could be worse if the drug is taken when the teeth are developing.