sores on my daughter's legs

My daughter is 11 years old and doesn't have a history of dermatitis or anything like that. Every summer she gets what looks like mosquito bites on her legs ( only 2-3 to start with ) but as the summer goes along she'll get more and more and the first ones will still be there at the end of summer. They are red and itchy. They never have pus in them. When she was about 4 yrs. old her pediatrician said he thought it was impetigo so we treated it as that but the creams he gave didn't help at all. He also did bloodwork and everything came back normal. All the sores will eventually go away during the winter but will be back the next summer. Do you have any ideas as to what this could be? or any suggestions on creams I could try? I am really getting concerned because they are starting to leave scars on her legs. One more thing, this year all the sores have been on her right leg, she might have 1 on her left ankle but other than that their all on the right leg ( she probally has about 20 sores on there right now.) Any insight will be greatly appreciated.   Thanks so much, Brandy