The Past Couple Of Days I Have Had Red Blotches

The past couple of days I have had red blotches appear all over my forearms. They tend to show up and get hot but not itchy, then slowly go away after about an hour or so. In the last three days this has happened about 7 or 8 times. I have no other symptoms, could this mean I am allergic to a certain thing?? They blotches are just red and hot, they do not itch nor are they swollen.