A Mother And Her Two Young Boys, Ages 4 And

A mother and her two young boys, ages 4 and 6 reside in a homeless shelter in which there are several other children. One of the boys has been continually bitten by something since early January. After a trip to the ER we are no closer to identifying the bites. There are no visible "bugs" in their suite other than roaches. The bites whelp like mosquito bites and look similar to brown recluse spider bites but do not deteriorate or turn another color. They do however, leave behind a pimple that resembles chicken pox. It does not itch. Any suggestions?