Why do I get red itchy feet when I stand?

[Millie147]

For a few years now, most times when I stand up in over 22-5 degree Celsius heat ish, my feet start to go red and itchy after 5-10 minutes? It's always the top of my feet and a red, flat, itchy rash occurs. This can often also occur under my knees and is almost mottled looking. Sometimes in extreme heat, such as hot showers, I can get the rash all the way up my legs and even on my chest, however these areas do not tend to be as itchy. This only ever occurs when standing up statically, if I walk the symptoms diminish. An aching sensation in my knees can often occur as well. This usually does not occur too often as I live in the U.K. and it is very mild thank god, but now that it's summer I have been struggling a lot more, even laying down in bed with the fan on my feet, despite the rash having disappeared, my feet are still itchy. I went to the doctors about a year ago and was sent to an immunology clinic but they couldn't figure out what it was. Please help, I just want to know what this is so I can get it treated :(

[SassyLassie]

Hello~I suggest seeing either your GP or a dermatologist. I really don't know what could be causing the problem unless it is a type of allergy to heat, which can happen.