Skin irritation help!

Here’s my issue: I have incredibly sensitive skin. Every time I go out for a run, I end up with this awful redness on my thighs and around my glutes. It eventually starts burning so badly that even just walking around becomes a massive pain. I tried wearing boxers under my gear, which helps a tiny bit, but the irritation still shows up. I’ve messed around with all sorts of creams and powders too, but nothing actually works. I deal with the exact same thing in the summer after spending time at the beach. Does anyone else deal with this? Better yet, does anyone actually have a solution that works?

By the way, before anyone tries to suggest hygiene—I shower multiple times a day. So if you're thinking this is because I'm dirty, you're wrong.

Thanks in advance