Self-conscious people blush more often, especially socially anxious or shy people.
I think the psychology for this, though maybe quite self-explanatory to some, is that socially anxious or shy people pay more attention to what others say about them. Because of their higher sensitivity to other people’s comment, they’re also more likely to have stronger reactions such as feeling embarrassed or shamed.
According to an article I am reading on this, it says that blushing is a reaction to a flight-or-fight response. The flight-or-fight response is an automatic process of our nervous system that helps us get away from dangerous situations or to aggressively approach them. When the fight-or-flight response kicks in, veins in our face dilate allowing more blood to flow in. This causes the redness in the face resulting in a blush.
Overblushing, or blushing in almost any social situation, is known as idiopathic craniofacial erythema, and can lead to hampered social interactions and isolation.