An allergic reaction?

Last Monday Stephen threw up (while in his car seat). I got it cleaned up, and he was fine the rest of the day. Last night he threw up four times in a period of an hour and a half or so before he went to bed. Today he is his usual happy self. The only similarity I could think of was that he had sweet potatoes both days. I googled "sweet potato allergy" and found that other babies had also vomited after eating this food. Also, without going into too many details, I know that he managed to keep the green beans down that he ate last night. So...we'll be avoiding sweet potatoes, and hopefully our little boy won't be throwing up anytime soon. Not a fun sight to see or clean up after.