Hi, My Brother Is In Bed Complaining Of Light-headedness, Nausea

Hi, my brother is in bed complaining of light-headedness, nausea and a numb, metallic feeling in his mouth. I think he also has a fever. Symptoms started last night, and he's still not feeling better. He said he might have poisoned himself with his WaterPik?? (he just bought a new and used it for the first time. Apparently, it's stored with some kind of chemical in it that you have to flush out first, and he thinks maybe he didn't clean it out properly before he used it). Could this be the cause? Or maybe food poisoning? What can we do for him?