Blotchy skin after a shower

I've noticed that every time I get out of the shower I have lots of red spots on my upper left arm. It's usually after a warm shower and it goes away around 15 minutes after I get out of the shower. It's not particularly dry or itchy. I haven't noticed these spots anywhere else. I don't know if it is actually something to do with my skin or underlying structures such as the capillaries or something. I have suffered with eczema for the past 20 years and I'm pretty certain it's not that. Does anyone have any idea what could be causing this? Thanks in advance!

[Dr_Aparna]

Hi,
This could be an allergic reaction to the hot water, allergies are common in people with a history of eczema.

A physical urticaria   is a skin rash brought on by a hypersensitive reaction to body heat. Symptoms follow any stimulus to sweat such as exercise , heat from the sun (which could also indicate solar urticaria), saunas, hot showers .

The affected area will often feel warm and can be extremely itchy or exhibit a burning sensation. Typically the rash occurs on the upper trunk and the arms but can appear on other parts of the body.

There is some evidence that in at least some individuals the condition is hereditary.THe treatment is with  antihistamines such as loratadine (Claritin), hydroxyzine, cetirizine.
However they are not indicated in your case since they go away, which is quite typical of this condition.
ref:http://en.wikipedia.org/wiki/Cholinergic_urticaria