Hello I Have An 8 Year Old Girl Who Keeps

Hello i have an 8 year old girl who keeps getting hives for no reason also sometimes her upper lip swells and she seems to be tired a lot. I know it is not the detergent i use because it happens when she stays at grandmas where she wears the clothes there that have been washed in different detergent. She has also worn new things and it has happened. She has also had a slight fever on and off early on. This has been going on for about 3 weeks. Nothing has changed in what she eats or drinks. What are your thoughts??