It's getting cold, and there is a rash on the inner thigh. Every time the bed gets warm, it itches, and the rash turns red and slightly bigger, but it won't be in cold air.

Hello, your condition belongs to allergic urticaria caused by air transformation.

The most prominent manifestation of urticaria is that the skin suddenly itches, and then there is a flat air mass higher than the skin, some red and some white, with more and more sizes and shapes, but the boundaries are clear, accompanied by itching, which is aggravated at night. The attack time is uncertain. The wind mass gradually spreads, and the doubts merge into pieces, which can be confined to a certain part or spread all over the body.

If your condition becomes more and more serious, I suggest you consider going to the hospital regularly and then carrying out relevant treatment.