My 20-month-old grandson broke out in hives today. They originally were only on one side of the torso, but have spread to all over the abdomen and chest Within the last 2 hours, his knees have become red and swollen. Non of these symptoms seem to be painful. He is happy and playful, with no apparent fever. So far, there have been no breathing issues. The family's yard was sprayed to kill mosquitos today, but previous sprayings have not produced any symptoms. Your thoughts?