What Causes Swelling In Feet And Ankle?

after spending the day outside my 10 yr. old daughter was covered in mosquito bites all over. That evening we noticed her foot had become swollen around her ankle and heel twice the normal size and she complained of a headache and had a low grade fever. Benodryl did not seem to help the swelling which lasted about four days. Headache only lasted that night but she is still running a low grade fever. Was this caused by a mosquito bite? Any reason to be alarmed? She has reacted to what I thought were mosqito bites twice befire where her leg swelled to the point she could not bend it and once in her arm. Doctor said to keep Benodryl on hand. She never reacted with headache and fever before.