Is Swallowing Some Clear Fluid From AA Battery Concerning?

my 3yr old chewed on the tip of a AA battery and leaked some clear fluid from it and he had swallowed some. He didnt get a burning feeling from it cause he didnt cry at all but I called the posion control center and they asked me if he had any redness or blister like bumps in his mouth and if he was in any pain. I checked for any redness and blister like bumps but found none and also told them he had no pain. they told me to just give him something to drink and hif he had a loss of appitite and didnt want to drink as much and had lots of drooling that he will need to go to the ER. My question is, is battery liquid or acid harmful when licked or swallowed if so when will I know when to go to a hospital if really serious?