People with auburn hair will have some of both. Skin and hair colour often go together, but not always. For instance, people with red hair are usually fairly pale skinned, they don’t tend to tan, they burn in the sun and are more likely to have freckles. There are exceptions however to this rule. Some people, with apparently jet black hair, also have very pale skin and freckle.

Several years ago it was discovered that the melanocortin 1 receptor, a protein encoded by a gene previously discovered in mice, was responsible for the production of red hair in humans. Everybody has two copies of this gene but there are slight changes in the gene that are very common in European populations.

If you have one of about four or five common changes in this gene and, one of these changes are found on both of your chromosomes, then you are likely to have red hair. A little bit of basic genetics; you have two copies of every gene, you inherit one from your mother and one from your father. If both of these genes are different, with respect to the changes that might lead to red hair, then you will have red hair. If however you only have one change, you have an increased chance of having red hair but it is not certain that you will have red hair.

Such a type of inheritance is described to by geneticists as an autosomal mode of inheritance. This means, in practice, that both your parents may not have red hair, but both could be carriers for the gene for red hair. If this was the case, perhaps one in four of children might have red hair. If one of the parents has bright red hair, and therefore carries two of the changes (one on each of their chromosomes), and the other parent is a carrier, then perhaps 50% of the children might have red hair.

It is this aspect of genetics, and the mode of inheritance, that explains why hair color might skip generations. There are different sorts of red hair. Some people seem to have what we call “strawberry blonde”, some bright red and some auburn. As far as we know, the genetics underlying these differences are fairly similar, in that changes in the gene referred to above, seem to be important for all sorts of red hair. However, if you have bright red hair it seems you are much more likely to carry two different copies of the gene than if you are a strawberry blonde.

There are some other puzzles about red hair. Some men might have red beards but dark colored hair. This is not entirely surprising as in many mammals the front of the body is a slightly different color to the back. In some animals, the molecular basis of this is clearly understood, as in these animals, they produce a different protein that seems to have the opposite effects to the red hair gene mentioned above. In man, we don’t think this is the case, but we also observed that people who do have red beards are more likely to carry at least one different copy of the red hair gene.

Another puzzle is why hair color changes so much during life. Most people are aware that hair color tends to be lighter at birth and gets darker, particularly during adolescence and puberty. Apart from saying that the cells that produce melanin become more active at this period we don’t understand why this is. Similarly, of course, we don’t really understand greying and lightening of the hair in old age. People with red hair often have different colored hair at different times of their life. It seems that it is more likely to be red in childhood or in early adult life, than in later life.

One medical importance of red hair is that individuals with red hair are, on average, more likely to burn in the sun and they are at an increased risk of skin cancer. The sensible advice seems to remain that since it is painful and uncomfortable to burn repeatedly in the sun, it is sensible to alter your behavior such that you don’t suffer the discomfort! On the other hand the risks of skin cancer should also be put in context.

For instance if you have red hair, the medical risks don’t compare with the far greater and much more serious risks from smoking and drinking large amounts of alcohol or being very grossly overweight.