Hello, thank you for posting your question. Fever, loose motions and vomiting in a 3 year old are most commonly suggestive of a viral infection of the intestine. This is a self limiting condition and no treatment is needed for the infection. The treatment mainly needs to be directed towards prevent dehydration. This can be done by replenishing every loose stool with a glass full of rehydrating solution like O.R.S or home made lemon juice/rice water etc. with a pinch of salt. Apart from that monitoring of the hydration status by keeping a watch on the urine output and mental status ( whether lethargic/irritable) should be done. Along with these probiotics like lactobacillus suspensions and zinc supplements are also found to be helpful. However, if your child has blood in stool, high grade fever( 102 degree Fahrenheit ) or toxic look, it would suggest that the cause is probably bacterial. In such cases a course of antibiotics is needed. If you need any more information regarding this case, do write back.