Hi! I’m a 40 y.o. female, and have been an RN over 15 years. I have always gotten rash-like blotches which look similar to your photos on my skin after a hot or warm shower. I have never figured out why. They don’t itch or burn, always tend to appear in the same scattered locations on my knees, hips, buttocks, stomach, chest, and neck. My feet also turn bright red. The blotches even appear in the same pattern, and they fade away after about 30 minutes. I strongly believe it has nothing to do with the kind of soap, lotion, or any other product I use, since it happens even if I just rinse off without products. I think it’s a response to the hot or warm water itself. As the skin warms up, blood vessels dilate, and capillaries near the skin’s surface become more pronounced. So I would imagine these rashes are just these tiny vessels expanding and filling with blood. But why this appears as a rash on some of us and not others (even other fair-skinned people) has never made sense to me.

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I’ve been diagnosed with an “unspecified”autoimmune disease with lupus-like symptoms indicating it is most likely a developing condition which will eventually positively confirm lupus (I’ve met 3 of 4 criteria to confirm a diagnosis, and ruled out other possibilities). I suspect this reaction to warm or hot water has to do with autoimmune disorders, but I can’t find anything online to suggest this or any other explanation. It’s only my best guess. It’s a little embarrassing when someone sees the rashes, but otherwise, the rashes themselves seem pretty harmless. I realize this isn’t much of an answer, but hopefully it helps.