Mosquito saliva isn't actually poisonous or anything, it just generates an allergic reaction due to its contact with your blood stream (the proteins and stuff). Same way your immune system tries to fight off anything foreign in your system. I'm pretty sure your body wouldn't have any problem digesting it.
Which does beg the question, I wonder if sucking the mosquito saliva wouldn't actually work? I think the primary obstacles would be: 1) it's usually too late by the time you notice (the inflammatory response has already started/the wound by the mosquito has already closed up), and 2) you couldn't suck up all of the saliva in the first place so the reaction would happen anyway. I'm not that familiar with medicine/human immune systems but a third issue might be that even if someone sucks up the mosquito saliva, since another human's saliva is still just as much of a foreign substance anyway you'd still have an allergic reaction just the same.
Anyway, as for the manga itself, haha yeah I really love Nekomura's Akaga. On the one hand, Kaga's just so in love with Akagi that these kind of teases are freakin' amazing. I dunno whether to be jealous or feel sorry for her, lol.