Hello, Enamel can be damaged by acid in the mouth. The stomach acid included in vomit with repeat episodes can easily damage the enamel on teeth. This would occur after the teeth are errupted and have been exposed to the acidic environment. This could then be the case with the baby teeth. Now you state the adult teeth have weak enamel. This could be a genetic weakness. Nutrition and medication taken while the teeth are forming will affect the quality of the tooth structure. Baby teeth can be damaged if baby sleeps with a bottle with milk products coating teeth and causing decay. Flouride can be given with children s vitamins to strengthen the formation of the tooth while developing. As adults the addition of flouride is not recommended because teeth are already formed. Instead, topical flouride can help strengthen formed tooth enamel. Too much fluoride taken as a child can have the reverse effect of weakened enamel forming. Often white spots are seen and indicate too much fluoride. The antibiotic Tetracycline is known to darken the layer under enamel and cause grey to brown banding if taken while teeth are forming. No concern with this type of discoloration when taken as an adult. The medication, Pizotifen, does not report any significant dental side affects concerning enamel. This is not available in the United States, so I am not familar with this drug for my patients. Drugs can have interactions and you can question your pediatrician with this concern. Can you tell me why as a child, this medication was recommended? Were migraine headaches determined to be the cause of his vomiting? I am glad to hear he is feeling better. Enamel is precious. Avoid an acidic diet and abrasive brushing techniques. Regular dental exams will check for enamel weakness as these areas will be more prone to decay. Rinsing with flouride may strenghten enamel. Restorative procedures maybe recommended such as bonding or crowns to replace damaged enamel. I hope my recommendations are helpful to you and I will be glad to provide additional answers if you have more concerns. Thank you for your inquiry.