Why does only my right side of face get red and hot?

Rosacea. Rosacea often flares when something causes the blood vessels in the face to expand, which causes redness. Things that cause a flare-up are called triggers. Common triggers are exercise, sun and wind exposure, hot weather, stress, spicy foods, alcohol, and hot baths. Swings in temperature from hot to cold or cold to hot can also cause a flare-up of rosacea.