The blush raises many questions which have proved difficult to answer. Why should an emotional response take this particular form? What use, if any, does a blush have? Why does it increase our visibility when we would least like to be seen? What are the psychological implications of the natural variation in skin pigmentation that renders the blush more or less noticeable? What is its physiological basis and how does this differ from the processes underlying, for example, anger or indignation?  Whereas signs of fear such as pallor, trembling and ‘butterflies in the stomach’ seem understandable in terms of the body’s preparation for action the utility of reddening of the face and increased skin temperature is not so evident. There are additional fundamental questions. Is the blush a unitary phenomenon or are there distinct forms? Perhaps we are misled by language. Perhaps the word blush is used in everyday language to cover more than one psychological or psychophysiological reaction and we will only understand these if we distinguish between them. Are blushing and flushing distinct phenomena or simply different names for the same thing? There are many basic questions here and scientific research is beginning to address these. It is fair to say that there is as yet no consensus on answers.

Where there does seem be consensus is that most people dislike their blushing. It is associated with mental confusion, unpleasant social predicaments and uncertainty how to behave in social situations and the blusher believes that it creates an impression of lack of poise or immaturity. The involuntary and uncontrollable nature of the blush contributes to this sense of being unable to cope. This can lead people who believe that they are prone to blush to avoid situations where they anticipate they might do; this curtails their social life, can create anxiety and can be associated with psychological problems. In psychiatric diagnosis blushing is considered to be a symptom of Social Anxiety Disorder and many sufferers have been prepared to undergo major surgery on their sympathetic nervous system in order to prevent their reddening despite the unpleasant side effects that can result from the procedure, for example compensatory sweating. Many who are anxious about blushing believe that their propensity to do so is the source of their problems rather than a symptom of them and are convinced that eradication of reddening would provide the solution. More research is needed into the experience of chronic blushers. They do not seem to differ in obvious ways on psychophysiological measures in embarrassment-inducing situations in the psychological laboratory nevertheless they may be more likely to than others to blush more frequently or  to do so in those where a blush is not usually called for and is therefore more likely to cause distress.

But are we correct to think of the blush in solely negative terms? This brings us back to the question of the functions, if any, a blush serves. Bodily reactions that give rise to unpleasant experiences can nevertheless have vital protective purposes, for example in the case of fear or pain. To show that you are frightened or in pain can bring people to your assistance. Social psychologists argue that embarrassment – which is a common trigger of a blush – is useful. It is useful for society in proving a relatively painless means of ensuring that we adhere to social norms; the fear of embarrassment keeps us in line most of the time. It is helpful in specific social encounters by enabling participants to overcome temporary difficulties that might otherwise disrupt or dissolve relationships. It is helpful for individuals by indicating to others their acknowledgement of social norms and their willingness to adhere to them, and hence their acceptability to the group. From this perspective, if there was no embarrassment there would be more aggression and social rejection; the shameless, brazen, ‘unblushing’ person is not someone whose company we would necessarily seek out.  Is this where the functions of the blush are to be found? When someone gets something wrong, perhaps by saying something that is unintentionally offensive or by being in the wrong place at the wrong time, an apology often is sufficient to diffuse the situation and shows that we are behaving out of character. A blush is helpful here because it is uncontrollable. We can apologise or smile without meaning it but we cannot control our blush. Hence it is an effective form of apology because it is sincere.

Psychological research shows that participants who are seen to blush after having infringed a social norm, for example by knocking over a pile of cans in a supermarket, tend to be judged less harshly than those who carry out the same action but fail to blush. A visible blush seems to enhance the observer’s impression that the individual is ashamed, embarrassed and concerned about others’ opinions and, again, its uncontrollability may contribute to this judgment. This is not always the case and a research programme undertaken by Peter de Jong and his colleagues suggests that in ambiguous circumstances where people’s motives are unclear, for example when they cannot produce a travel ticket when the collector asks for it, their blush tends to be perceived as a sign of guilt and they are not viewed positively. Clearly the social context will affect observers’ interpretations of reddening. We also blush in the absence of a transgression or mishap, particularly when something happens to suggest that something is likely to be revealed about us that we would prefer not to become known, and in these circumstances the blush might actually produce the predicament or negative judgments we fear. This might be a cost that has to be borne to preserve the social value of a blush.

Some theorists locate such observations within an evolutionary framework. Evolutionary explanations of shame regard its expression and action tendencies – gaze aversion, a shrinking posture, hiding the face, fleeing – as appeasement displays that signal to dominant individuals that the individual occupies and accepts a subordinate position in the group. Appeasement displays are common among primates and the blush might be an equivalent in humans and serve as a nonverbal form of apology and offer of remediation, all the more effective because the involuntary nature of the signal means that it cannot be feigned and hence will be judged to be sincere. We have no direct evidence on this and no indication whether the blush serves similar functions across cultures or among people with different skin complexions or pigmentation. Nevertheless, perhaps the transient unpleasantness of the blush is a price worth paying for the wider and longer-term benefits for society and indeed for the individual blusher.