Additionally to stress and social situations there are other things that may cause blushing for certain people.

CoffeeA cup of Coffee
Caffeine-containing drinks such as strong coffee and lots of cups of tea can stimulate the body’s natural sweating mechanism and blushing. Heat and caffeine make you blush a lot easier. If you need caffeine I found Red Bull to be the best. Lack of sleep my put you in a calm mood, but this is very individual, some people blusher more.