I had a real bad experience once. I was moving from Florida to Canada and wanted to bring my 4 year old Puffer with me. The airline had told me it should be no problem, that I just needed to fill out paper work at the airport and to come early. Long story short, I was not allowed to take him and had to choose between leaving him at the airport with customs or missing my flight which I could not do...I have no idea what happened to him
I called to try to find out once I landed but I never got an answer...Im not sure about going to Brazil but if you are travelling through the US to get there or Mexico, I doubt it is possible without permits and you for sure will not be able to take them to your seat, gauranteed. They are not allowing ANY exceptions. They just barely let my fiance take her asthma puffer with her after making her take a puff.