Any persistant vomiting that you are describing is reflux, it is because the lower oesophegeal sphincter is loose and allows stomach contents to go upwards, unless your child is refluxing at the time of the barium swallow then it is not a conclusive test for reflux, and I know many babies who have had a clear barium swallow and still have reflux.

That being said if your baby is not in any pain, then there is no need to medicate, it is then classified happy spitter (well not so happy for you) but basically it is the same as normal reflux and hopefully by 12 months the sphincter will have strengthened enough to keep stuff down.

If your bub has been hospitalised for it, then I would think though that you should get the acid levels checked and ask about a pH probe. I know first hand about how doctors can misdiagnose this and it can get to a stage where there is no weight gain and food aversions from it.

Thickeners may help keep it down, you could try changing the formula to a hypoallergenic one, like the Nan HA, or get a script for Neocate. He could have an intolerence to milk, so the more hypoallergenic ones digest quicker so there is less in his tummy to vomit.

The other thing to rule out if it is definately not reflux is a milk allergy or an emptying problem, there is a test called a gastric emptying study and this determines how fast the food goes through their system, some kids digest really slow, so if they vomit it will come up hours later, there is medication, domperidone that can help move the food through quicker.

I suppose that is everything, good luck, it is really hard when they are loosing weight and sick and no one can give you a postive answer, if in doubt ask to see a peadiatric gastroenterologist they generally have a lot of suggestions.