Beauty is only skin deep is a saying that means that a person's physical appearance does not determine who the individual is. The expression is commonly used as a reminder that a person may look attractive, but she may not have attractive inner qualities. It is also used to say that a person may not be the prettiest to the eyes, but she may be very attractive because of her personality.
It is common to hear the saying "beauty is only skin deep" in the United States. The saying exposes a tendency for individuals to judge one another primarily by their physical appearance. Doing this often leads to disappointment and surprise, as one person may judge another and be completely wrong. For example, a man may encounter a stunning woman in a bar, and he may draw a number of conclusions about the type of person she is. Upon getting to know her, however, he may find that her negative characteristics are so dominant that they overshadow her physical appeal.
The idea that beauty is only skin deep can also be used to the opposite extreme. There may be situations where a person's physical beauty is altered by aging, disfigurement, or other circumstances. Yet her positive inner qualities may remain the same. There may also be instances where a person may have never been physically appealing, but upon getting to know her it is discovered that her inner qualities are more attractive than her physical appearance.
This saying may be used when trying to communicate a number of lessons. In some situations, the person who says it may be trying to tell a person that his basis for judgment is flawed and he needs to look at qualities other than appearance. This expression may also be used when speaking to an individual who relies primarily on her beauty to attract attention. The lesson in this case may be that appearance will help a person to only a certain degree. Beyond that, if she does not have other qualities, she is likely to have opportunities that appear to be opening initially but that she is unable to sustain.
As beauty is a word that is most commonly associated with femininity, the expression "beauty is only skin deep" tends to be most commonly used when talking about females. It can, however, be used when referring to the differences between the outer and inner qualities of males. It is rarely, if ever, used when talking about animals or inanimate objects.