What Causes Insect Bite Like Painful Blister On Knee?

My daughter is in Haiti right now and complained of a rash, but now she is complaining of bites that seem to be swelling. They look like pimples and are very sore to touch. She has one on her knee that is huge and making it difficult to walk. She says they have tried to drain it, but nothing comes out. Could these be spider bites?