Nooch was really poorly tonight - James walked him for about an hour whilst I made dinner - off lead although still velcroed to leg

Anyhow they came back and nach has waggy tail as usual....
ten minutes later he is demon dog - pawing the floor like he is digging a tunnel - hoovering the carpet with his ears - eyes swollen - hot spots everywhere. panting a lot
Barking and crying at me-took him out the back and examined him all over - could find nothing - no signs of anything - didnt know what to do - did my usual made it up as I went along. I stood him in cool bath to try and calm his paws and legs down - water everywhere

I gave him some antihistimane and about 30 minutes later he actually began to calm down.
All I can think of is that he was stung or was in something that he shouldnt have been in but no rash no sign of any entry points - any ideas

am I totally off the mark