About hair growth

Hair is made of keratin, a special protein which constitutes the basic material in our nails and can also be found in as a protective material in our skin. Each strand of hair has three layers; the outer layer is called the cortex and the inner layer, the medulla.

The outer layer is thin and uncoloured, and protects the thicker cortex, which contains melanin. Melanin gives hair its colour, so your hair colour depends on the type of melanin you have. There are two types of melanin; eumelanin which results in brown or black hair and pheomelanin which gives a red colour. You’ll have blonde hair if you have very small amounts of melanin. Grey hair is the result of a shortage in melanin, which usually comes with age, although it can also be caused by stress or illness. The innermost layer of hair is called the medulla, which reflects light and gives hair its colour. That’s why hair colour looks different in sunlight than in the shade.

The shape of the cortex determines whether hair is straight or curly. If the diameter of the hair appears round, the hair will be straight, if the cortex is oval in shape, the hair will be curly.

We distinguish between two types of hair: Vellus hair, ”baby hair”, which is fine, colourless and almost invisible, and hair which is darker and more visible, which is called terminal hair. Terminal hair is the hair we’re referring to when we talk about hair generally. The hair follicle produces the hair and is therefore what decides whether it is vellus or terminal hair. When hair falls out, the thick terminal hair is often replaced with thin vellus hair. It is the result of physical damage to the hair follicle, which can then no longer produce terminal hair.

On average, we have 5 million hairs, of which around 100 000-150 000 are on our heads. Blondes have the most with around 140 000, brunettes have around 105 000 and red-heads around 90 000.

Hair grows in cycles made up of three phases: anagen, katagen and telogen.

Anagen – This growth period lasts two to eight years. During the anagen phase, the cells in the root divide quickly and make the hair’s surface, which becomes keratinised. At the same time, the hair follicle grows into the skin’s deeper layer (the dermis) to get its nourishment. People who have a long anagen growth phase can grow very long hair, while those with a shorter anagen phase will never be able to grow really long hair. Hair grows at around 1.25 cm a month, so that uncut hair can grow to 30-120 cm in length.

Katagen - After the anagen phase is a two to four week katagen phase. This is when hair is renewed. The root reduces and the hair stops growing, but does not fall out. During the katagen phase, the hair follicle shrinks to around 1/6 of its normal size. The deepest section is destroyed, the root loses its blood supply and the hair is pushed upwards.

Telogen – The hair follicle then goes into a telogen or dormant phase for two to four months. During this period, the hair doesn’t grow, but remains in contact with the hair follicle while the root rests. About 10-15% of all hair is in the telogen phase at any one time. After the telogen phase, the cycle is complete and the hair returns to the anagen phase. During this time, a new hair exterior is formed and the old hair is pushed upwards and falls out.

About hair loss

You lose around 50-100 hairs a day from natural hair growth. This is normal hair loss that you see every day in the shower and when you comb your hair. In healthy hair follicles, this hair is quickly replaced with new hair.

There are a lot of factors which can affect normal hair growth and cause temporary or permanent hair loss, e.g. some medications, radiation, chemotherapy, exposure to certain chemicals, hormonal factors, diet, thyroid disorders, certain skin illnesses and stress.

Some of the more common causes of hair loss are given below.

Hormones

Since hormones both stimulate hair growth and cause hair loss, changes in the body’s hormone balance are the biggest factor affecting hair loss. Disruptions in hormone balance can affect both men and women.

Normal changes in the body’s hormone balance are the most common cause of thinning hair in men and women. In men, hair loss is usually concentrated in a particular area of the scalp and follows a particular pattern, known as androgenic alopecia.

Androgenic alopecia can also affect women, although women usually experience thinner hair all over the head without it following any particular pattern. Androgenic alopecia is caused by the androgen dihydrotestosterone, DHT. All people have DHT, which is made by the body, but only a few experience hair loss. People suffering hair loss have hair follicles with more androgenous receptors than DHT can take a hold in. Antiandrogenous medicines are now available which block DHT production and can prevent hair loss.

Childbirth

Following pregnancy, many women experience hair loss, caused by lots of their hair going into the dormant phase at the same time. Two to three months after the birth of their baby, some women notice large amounts of hair in their hairbrush or comb. This can usually last for up to six months before stopping altogether. The condition is caused by normal hormone changes in the woman’s body after childbirth.

Birth control pills

Women who are genetically more likely to be affected by androgen alopecia, also known as male hair loss, can start losing their hair a lot earlier if they take birth control pills. Hormone changes caused by ”the Pill” can trigger hair loss. If a female member of the family suffers from hair loss, you should tell your doctor before being prescribed the Pill. Some women can experience hair loss when they stop taking the Pill, which usually starts 2-3 months afterwards. This can go on for around 6 months before stopping. In some cases, the hair doesn’t recover and the woman is left with permanent hair loss.

Genes

As a rule, hair loss can only happen if you have specific, inherited genes. A gene is a piece of chemically-regulated, inherited information found inside a chromosome and is part of a person’s DNA. The genetics behind androgenic alopecia involve more than just one gene. These genes can be inherited from either the maternal or paternal side, although we do know that genes inherited from the maternal side can play a greater part in hair loss. In the future we will probably be able to engineer genes using gene therapy to protect the hair follicles from the hormone dihydrotestosterone. As things stand, however, we have not yet been able to identify the exact gene behind androgenic alopecia.

Illness

Since the hair follicle is very sensitive, it is easily affected by imbalances in the body. In the vast majority of cases, hair loss is caused by illness and the hair recovers by itself after the body has returned to a normal state of health.

Fevers, severe infections, heavy colds

After a long illness with a fever, severe infection or cold, you may notice some hair loss, which is usually only temporary and recovers by itself.

An overactive or underactive thyroid gland can cause hair loss. Thyroid gland disorders can usually be easily diagnosed by your GP with a blood test. Hair loss caused by a thyroid gland disorder usually recovers following the right treatment.

Poor nutrition

Some low protein diets or abnormal eating habits can cause protein deficiency. To conserve protein, the body stops growing hair, which goes into the dormant phase. Two or three months after the body becomes deficient in protein, large amounts of hair will start falling out. A sign of this happening is if the hair can be pulled out easily at the roots. The situation can be reversed and corrected by eating sufficient quantities of proteins. When we’re dieting, it’s very important that we eat enough protein.

Medicines

Some prescription drugs, such as gout, rheumatism, anti-depression, heart, blood pressure, and blood-thinning medicines can cause temporary hair loss in some people. High doses of vitamin A can also cause hair loss.

Cancer treatment

Chemotherapy and radiotherapy cause hair loss since they stop the hair cells from dividing. The hair becomes thinner and falls out when it’s pushed out through the scalp. It starts happening 1-3 weeks after treatment. Patients can lose up to 90 percent of their hair. Once the treatment has stopped, the hair regrows.

Iron deficiency

In some cases a lack of iron can cause hair loss. Some people don’t have enough iron in their diet and some people can’t absorb iron at all. Women who suffer heavy periods can develop an iron deficiency. Low iron levels can be detected by a blood test and corrected with iron tablets.

Operations/chronic illnesses

People who need to undergo major surgery can experience increased hair loss 1-3 month later. The problem rectifies itself within a few months. People suffering from a chronic illness can also experience increased hair loss.

Alopecia areata

Hair loss due to alopecia areata is most likely caused by the immune system’s reaction to hair follicles. Hair usually falls out in just a small area, causing a completely bald round patch. In more serious cases, i.e. alopecia totalis, all the hair all over the body falls out, including eyebrows and eyelashes. Treatment includes localised creams, light therapy and, in some cases, medication.

Fungal infection

A fungal infection starts with small hairless patches, which can spread and cause redness and swelling. This contagious illness is most common among children and can be treated with medication.

Stress

Stress can cause hair loss among people. Usually, hair loss is experienced within 3 months of a stressful event and it can take about 3 months before starting to recover. In the vast majority of cases, hair loss caused by stress is temporary, although if the person is genetically prone to hair loss, stress can make the situation worse.

Mechanical damage

Damaged hair can also be caused by ourselves, either deliberately or unintentionally. Some people pull their hair when they’re stressed, causing the hair to fall out. Some hair treatments such as colouring, bleaching and perming can also damage hair and cause it to fall out.

Hair pulling or trichotillomania

Some children and even some adults play with their hair by pulling it and twisting it. It can be part of a behavioural problem or a bad habit, often done unconsciously. If the habit isn’t broken, permanent hair loss can result due to the constant stress on the hair follicles. The best way to solve the problem is to seek help from a professional psychiatrist.

Hairstyling

Lots of people like to change their hair with chemical treatments such as colouring, bleaching and perming. If done correctly with good quality products, the hair won’t be damaged to any significant extent. However, the hair can become weaker and break if such treatments are carried out too often. The hair can also break if the preparation is left in the hair too long, if two treatments are carried out on the same day or, for example, if bleach is used on already bleached hair. Some of these preparations contain very strong chemicals and there have been cases where the chemical has burnt the scalp resulting in permanent hair loss. If possible, always use a qualified hairdresser. If you do the treatment yourself, use reputable products and read the product information carefully.

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