Although Charles Darwin once dubbed blushing "the most peculiar and most human of all expressions,” scientists have yet to figure out what exactly causes some people to blush.
While blushing is often confused with flushing, the two problems have very distinct differences. Flushing generally extends over more of the face and onto the neck and upper chest. It also typically has an identifiable physical cause, such as rosacea, menopause, carcinoioid syndrome, or a negative reaction to certain types of prescription medications. In comparison, blushing is limited to the cheeks and triggered by embarrassment or anxiety.
From a physiological standpoint, blushing occurs in the face because, per square millimeter, facial skin has more capillary loops, as well as more vessels per unit volume than other parts of the body. Also, the cheeks' blood vessels tend to have a wider diameter and are closer to the surface of the skin. The fluid in the tissue of the cheeks don't tend to obscure the blood vessels as much as in other parts of the body. When the body is faced with stress, the “fight or flight” responses kicks in and releases the extra adrenaline that stimulates the sympathetic nervous system to cause facial blushing.
Many different types of people experience problems with blushing, but the condition is more apparent on those with very pale complexions. Although women do tend to blush more often than men, they are also better at covering up their problem with skillful makeup application. Statistically, teenagers blush more often than adults, but scientists aren’t certain if this is caused by the hormonal changes of puberty or a lack of appropriate coping mechanisms for stressful situations.
While many people blush at some point in their lives, the condition can cause serious lifestyle problems for certain individuals. People who blush on a regular basis may become so embarrassed by their problem that they avoid potential triggers such as meeting new people, talking in front of large groups, or trying new activities. People who modify their daily activities based on a fear of blushing are said to suffer from erythrophobia—a term which literally means "fear of redness." People with erythrophobia will experience symptoms such as dry mouth, nausea, breathlessness, dizziness, heart palpitations, or excessive sweating when faced with a situation that has caused them to blush profusely in the past. Since erythrophobia is linked to social anxiety disorder, the condition is typically treated in much the same way.
Some people even suffer from a disorder known as idiopathic craniofacial erythema, which causes them to blush with little or no provocation. This condition is generally treated with cognitive behavioral therapy, although more extreme cases can be sometimes helped by a surgical procedure called Endoscopic Transthoracic Sympathicotomy, in which certain portions of the sympathetic nerve trunk are burned, removed, severed, or clamped to prevent the blush reflex.