my 12 month old woke up with 2-3 inch red spots on his legs yesterday after his nap. this morning they were gone from his leg but a new one was on his other leg even bigger. he just woke up from his afternoon nap and that one is gone and now he has one that covers the whole back part of his calf. it doesn t seem to itch or bother him. we thought it was a spider bite initially but we started checking his bed for spiders before we put him in it and haven t found any. what can be causing this?