(Concern) I'm worried about sunlight allergy. Is there any treatment method?

I didn't have any skin conditions when I was young. However, a few years ago, I developed a sun allergy. If I am exposed to strong sunlight for more than 10 minutes in the afternoon, I get hives on my skin. It's very inconvenient because I have to wear a wide-brimmed hat and arm sleeves every time I go outside. The hospital said there is no suitable treatment. Does anyone know of any folk remedies or alternative treatments?