Face is red and blotchy after a warm shower, what can I do to help the redness go away? Take an antihistamine? No I don't have rosacea

Flushing of face. Common problem and related to (1) rapid dilation of superficial blood vessels called capillaries that increase in diameter and blood flow in response to heat. With dilation, the body cools down by running more blood through the surface of the skin and it transfers heat away from the body (2) release of chemicals in mast cells that an antihistamine could block if you take it regularly.
Worth a try. Some people do get quite blotchy and red after warm showers. This can be due to rosacea, certain viral infections, allergies, medications, and also simple genetics-esp if you're very fair skinned. If it's not causing you a problem i would suggest you do nothing at all. If you have to do something, antihistamines sometimes do help. Good luck!