When hair is top of the agenda
We spend a great deal of time and money on a part of our body that we can survive quite happily without – our hair. We are strongly attached to our vestigial fur, which also happens to give away a great deal about our lifestyle and is ideal for studying the development of cancer.
For some reason, our ancestors lost their fur. However, with the exception of our palms, soles, lips, eyelids, ear canals, nipples and certain genital areas, we still have hair covering our bodies.
Why, at some time in the past, we shed our fur is an unsolved mystery, although several attempts have been made to explain it. On of these suggests that our ancestors would have sweated profusely as they crossed the savanna, making the loss of body hair an evolutionary advantage. Another theory deals with the waste of energy involved in producing something we can survive without; if we are able to heat and protect ourselves without fur then why waste energy creating hair in large amounts.
Because, as noted, we can survive without body hair. Total hair loss does not in itself impact on physical health.
The hair we have managed to retain has survived the demon barber of evolution for a variety of reasons. Hair on the arms and legs can be viewed as vestigial, a remanent of another era much like the appendix. Nose hair and eyelashes fulfil a practical function in protecting our lungs and eyes. It is more difficult to understand why we have hair under our arms and around the genitals, although one theory is that this hair collects scent to attract a mate.
The hair on our heads protects against the sun but facial hair has no obvious practical benefits. It is also difficult to see why a protective layer of head hair would need to grow so quickly and be capable of attaining such length.
According to Lars Norlén, associate professor at the Dermatology Clinic at Karolinska University Hospital in Solna, it appears that head and facial hair once fulfilled some other purpose for us, probably a signalling function.
“In all probability, given that we have retained long hair on our heads, these functions have been very important. This also explains why scalp hair is linked to our identity and why a disease affecting the hair can be so psychologically stressful,” says Lars Norlén.
Naturally, we have no way of knowing what our ancestors communicated with their hair during those millions of years over which our own hair suit was being refined. But over the last few thousand years, head hair has been the subject of many strong feelings, often linked to attitudes to sexuality, religion and power.
Certainly, within the Judeo-Christian-Islamic tradition it has been considered important for married, and even unmarried, women to cover their hair when outside the home. In Catholicism, nuns have worn the veil to mark their marriage to God.
In the Roman Empire, women committing adultery had their hair shorn, as did women accused of having relationships with German troops in occupied Europe during World War II. Joan of Arc was sentenced to death, among other things for her cropped hair, which was seen as an exclusively male trait.
Buddhist monks and nuns shave their heads to demonstrate their devotion to the holy life. However, in Sikhism the same thing is expressed in precisely the opposite manner; neither head nor facial hair may be cut, symbolising spirituality.
According to Lars Norlén, it is in the shadow of these cultural attitudes that the suffering of involuntary hair loss must be understood.
The most common hair disease is alopecia areata, spot baldness, with hair falling out in round patches that can occur anywhere on the body. In rare cases, hair loss may be more comprehensive, with the loss of all head hair or all hair over the entire body. This disease can strike at any age and is believed to be an autoimmune attack on the hair follicles. It appears that the disease can be triggered by emotional stress.
Lars Norlén explains that it is this disease that has given rise to the idea that the hair can turn white overnight. This is because hair can fall out very suddenly over a couple of days, sometimes after a deeply stressful event and generally without warning. Oddly enough, it is normally those hairs that have lost their pigment that remain, giving the impression that the hair has turned white, as long as the hair of the individual in question has begun to turn grey or white prior to the onset of the disease.
Patients with spot baldness account for the majority of those Lars Norlén sees at the dermatology clinic. Another large group is those suffering from inflammatory hair disease, where the hair falls from painful and itchy areas of the scalp leaving scarring.
“Hair diseases are treated unfairly and often linked to cosmetic concerns. This has had an impact on how hair research is viewed, leaving us with many gaps in our basic knowledge about hair. For example, we do not know about the mechanisms behind hair growth and hair loss at a molecular level.
Several studies have demonstrated a negative impact on the quality of life for patients suffering hair loss. For example, being left without hair can cause feelings of shame and make it difficult to socialise, leading to isolation.
“For those working clinically with these patients, it is quite clear that their suffering can be great and very real. Few patients are as determined and treatment-motivated as hair patients,” says Lars Norlén.
Inflammatory hair disease is the most difficult to treat. In such cases, hair loss can be permanent in those areas where hair has fallen out, although it may be possible to prevent the spread of bald patches. One treatment involves dampening inflammation, for example using cortisone.
So, the detailed mechanisms behind hair loss remain unknown, irrespective of whether hair loss is a result of disease or normal aging. It is however clear that male hormones, androgens, play a major role in this context. Androgens cause facial, chest, pubic and underarm hair to grow during puberty. In women, this development is halted by the female hormone oestrogen, which is one reason why women have less body hair.
Later in life, the opposite occurs; in both genders it is the follicles’ exposure to androgens that causes them to remain in the growth phase for increasingly short periods. Finally, the follicles entirely cease to produce hair. As a result, fewer and fewer hairs grow on the scalp, leaving the hair thinner and thinner. In women, even this development is halted by oestrogen.
It is likely that changes in hormone levels are also behind many women having thicker manes during pregnancy. That many women experience a major loss of hair a few months after giving birth is assumed to be a result of the continuing changes in hormone levels and the great physical stress involved in giving birth.
“It is often physical stress, such as an operation or a serious infection with a high fever that causes hair loss, although emotional stress may also have an impact. Losing one’s hair due to stress is common enough to be viewed as a normal stress reaction – although we remain unable to explain how or why it happens,” says Lars Norlén.
We have somewhere between 100,000 and 150,000 hairs on our heads. Blondes have more hairs than brunettes, who have more than redheads.
The hair on the head grows more rapidly than body hair, at a rate of 11-16 millimetres each month. The rate of growth increases during warm, damp weather, possibly due to increased blood flow around the follicles. So, the hair grows more rapidly in summer than in winter – or if one moves from Sweden to somewhere such as Florida.
This is not news to Henrik Druid, forensic pathologist and professor at Karolinska Institutet’s Department of Oncology-Pathology. As the researcher that he is, he was unable to resist measuring his own children’s hair during a period the family spent living in Miami. And indeed, his monthly measurements showed that the children’s hair grew more rapidly in the warmer climate.
“The growth of hair on the scalp is relatively well described. This means that we can say with some exactitude when various segments of a hair are formed. Just 12 centimetres of hair can be enough for us to deduce something about how a person has lived for the past year,” says Henrik Druid.
A great deal, in principle everything that we consume leaves a trace in our hair. Via the blood or sweat, this is stored in the hair, the follicle or very close to the scalp. As the hair grows, the stored substances follow with it.
A single hair can therefore tell us a great deal about the person it has been plucked from. It is possible to see which sources of protein have been included in the diet and even background radiation leaves traces, offering hints as to where the person may have been purely geographically.
Hair cells do not have any blood circulation or other metabolism, so the cells in a hair can be considered as dead once they have left the follicle. A hair sample therefore breaks down very slowly and is equally useful whether taken from a living or dead person.
“We have samples that have been stored at room temperature for over 20 years. They will produce the same measurements today as when they were taken,” says Henrik Druid.
He works with something called sequential hair analysis, where a small tuft of hair is clipped into half-centimetre lengths. The presence of various substances is then investigated in each length. It is then possible to see whether, for example, someone has used narcotics, consumed alcohol or taken medication – including when they did so and whether their consumption has varied over time. A blood or urine sample offers only a snapshot of the moment the sample was taken.
There are examples of cases in which women have alleged that they were drugged and raped. A hair analysis has subsequently confirmed their story to the extent that it could be proven in court. There are also studies demonstrating that almost eight in ten drug addicts dying of an overdose do so during a relapse, after abstinence has lowered their tolerance for the drug in question. This has also been shown by hair analyses that revealed the break in drug use for a period prior to death.
“This is tragic, but important knowledge,” says Henrik Druid.
So, a hair sample can confirm the consumption of various substances and accurately date any such consumption. However, to draw conclusions about the amounts consumed has proved more difficult.
Many substances are stored in the hair’s melanin – the substance that gives hair its colour. Light, dark and redheaded individuals have different kinds of melanin in varying amounts in their hair, leading to variations in storage.
This means that the same amount of consumption can leave differing trace amounts depending on hair colour. Bleaching also affects the amount of melanin in the hair, and thus the stored trace amounts, something that makes the job of the forensic pathologist more difficult.
Not only that, but every substance has its own binding pattern.
“There are many difficulties involved in these measurements but if one compares an individual with themselves, it is possible to draw conclusions regarding levels in different segments. It is then possible to see whether consumption has increased or decreased,” says Henrik Druid.
Hair follicles are one of the few human organs that follow a cyclical rhythm. In the growth phase, follicles burrow deeper into the skin while at the same time a hair shoots up. The individual hair can then grow for two to eight years and the longer the period of growth, the longer the hair can grow. A shorter phase follows, two to four weeks during which the follicle shrinks. Finally, there is a resting phase during which the hair does not grow but normally remains in the follicle. When the individual hair does finally fall out, the follicle returns to the growth phase and creates a new hair. In accordance with this pattern we shed 50 to 100 hairs a day.
The mechanism behind this cycle is of interest to Maria Kasper, senior researcher at Karolinska Institutet’s Department of Biosciences and Nutrition. Of specific interest is what happens when a hair grows – or when a follicle is formed in an unborn embryo. This is because follicles cannot be created after the prenatal period; those we are born with are all we get.
The cells that Maria primarily studies are keratinocytes, a type of epithelial cell that can take on a variety of roles. For example, they may be part of our outer, visible layer of skin or be part of a follicle and, eventually, a hair. Maria Kasper wants to find out what controls this development in keratinocytes; what decides whether they are to become a skin cell or a hair cell and what happens when such a cell instead becomes a cancer cell. What differentiates these patterns of development and what controls them at a molecular level?
Maria Kasper and her colleagues follow individual cells in follicles in mice that are either healthy or bred to always develop skin cancer. Using a special technique called single cell sequencing, they are able to see exactly which genes are active in an individual keratinocyte. They are then able to follow the course of events in the mouse; what happens in skin cells that become sick – and what distinguishes those that remain healthy?
“We study the microenvironment around these cells. By that, we mean factors such as nearby blood and lymph vessels, as well as their proximity to other cells, such as nerve cells, fibroblasts or leukocytes. These are not evenly distributed around the body but rather they generally occur in groups. We want to find out how different cells affect one another. The intention is to understand what controls the ability of cells to replace cells in healthy tissue – and what makes them form tumours instead. We also want to understand what helps newly established tumours to grow larger,” she explains.
Text: Annika Lund, first published in Swedish in Medicinsk Vetenskap No 2/2018.
Hair – true or false?
- It is true that stress can turn hair grey. The widely disseminated before-and-after images showing the effects of Barack Obama’s terms in office, in which his hair goes from dark to grey, depict a realistic course of events; stress affects the loss of pigment in the hair. The mechanisms behind this are unknown.
- Redheads as a group appear to be harder to anaesthetise, requiring higher doses of narcotics. This claim has only been investigated in small-scale studies, according to which it appears to be true. The cause remains unknown.
- It is false that the hair continues to grow after death, although as the body dehydrates the skin may recede, giving the appearance that hair and nails have increased in length.
Sources: Martin Holmer, chair of the SFAI, and interviewed researchers.