Hello, Dehydration and thrush are definite possibilities. It is very imortant to keep well hydrated. Try only small amounts of liquid taken often( at 10 minute intervals) when nauseous. Try to replace electrolytes. Dehydration can be very serious if persists and cause stress to the entire body. Vomit is very acidic and irritating to the throat and mouth. Repeat, long term episodes can erode enamel. Thrush will need an anti-fungal treatment such as the prescription medicine Nystatin. Rinse with warm salt water. Keep up good oral hygiene. Make sure to be cleaning tongue. Try to keep up balanced vitamin intake especially vitamin B complex. Anti-inflammatory medicines, acetaminophen or ibuprofen, if tolerated, can reduce discomfort. The antihistamine, Benedryl, also is an anti-inflammatory medicine. Maintain proper nutrition as best as possible. Make sure you have thoroughly treated your son s condition. Did you have a diagnosis? Some conditions such as strep require an antibiotic which can disturb the balance of the normal oral bacteria. Thrush can be a typical response. oral compications with systemic viral and bacteria infections are common. Thank you for your inquiry. I am available to assist with additional questions. I hope your son is feeling much better and hope my answers have been helpful.