What Could Cause Allergic Bumps Around Thigh Which Looks Like Pimple?

Hi, I need to know what may possibly be happening to my 16 year old son. About a month ago we traveled from our home in New York to Disney World in Florida for a family vacation. While on vacation in FL, my son developed a rash on his neck that looked pinkish and blotchy that resembled hives. When we got back to NY, I took him to the walk-in and they gave him some type of allergy medicine that I later found out was suppose to go up his nose, and we had been putting it directly on his neck. However, the rash still disappeared although it took a while (whether it was due to the medicine or not we don t know). I doubt it because we were distributing it incorrectly. His doctor thought that the rash could have been a result of an antibiotic (Amoxicillin) that he was taking for facial acne. Although the rash disappeared after some time, he started breaking out with these bumps around the front and back of his thighs with several on the inside of his thighs that almost resembled infected pimples. He was also complaining of a sore scrotum but wouldn t show me because he is 16 and tried to tell me it was chaffing and needed Gold Bond, but I m not sure it it s related or not. There are also a couple on his lower belly area but the majority is around his thigh area. Do you have any suggestions on what this could be?