Twisted like a seashell, actress Kim Novak’s hairdo in Alfred Hitchcock’s 1958 film is an icon of the power of seduction of hair. The star’s platinum blonde topknot won the heart of the detective played by actor James Stewart, in a scene that is not restricted to movie screens. All over the world, full, glossy hair catches the eye of both men and women and is considered a symbol of youth, health and power. This is also true of the Brazilian researchers who are beginning to find out how cosmetics act on hair strands.
Just like the biblical character Samson, who lost his strength when Delilah cut his hair, progressive loss of hair lowers self-esteem, makes people feel less attractive and makes them socially reticent, a problem which, according to European studies, affects women and younger men more serioiusly. Besides being important to psychological well-being, says dermatologist Fabiane Mulinari Brenner, from the Federal University of Paraná (UFPR), hair is imbued with social and cultural significance. The style defined by a haircut or a hairdo indicates the person’s social group and sometimes identifies the person’s social standing. This is why military recruits, criminals and war prisoners are forced to shave their hair: it is a way of eliminating their individuality and subjugating them to authority, says U.S. psychologist Thomas Cash in an analysis of the topic published a while back.
In view of the large number of values ascribed to hair, it seems natural that people with attractive hair want to preserve it – and many people wish they could have hair like supermodel Gisele Bündchen or film star Rodrigo Santoro – with the help of shampoos, conditioners, and other beauty care. Of course the cosmetics industry has always identified this desire and invests heavily in the release of products that promise to restore the health of the strands or make hair thicker and glossier, as seen in women’s magazines or on TV commercials. Recent data published by Associação Brasileira da Indústria de Higiene Pessoal, Perfumaria e Cosméticos, the Brazilian cosmetics industry association, whose members are the biggest cosmetic companies, reasserts the commercial success of this industry: the production of hair care products grew by about 50% from 2003 to 2006, totaling 458 million tons, while sales more than doubled, reaching US$ 2.2 billion last year. But do all these products really work?
The answer provided by the studies conducted by research institutions with no connections to the industry has not always pleased cosmetics manufacturers. In some cases, it corroborates the impression that women have acquired after many years spent in hairdressing salons; in others, it destroys seductive myths built up by advertising campaigns. Tests conducted by the team of chemist Inés Joekes, from the State University of Campinas (Unicamp), show that shampoos and conditioners clean hair and makes combing it easier, but that they do not recover damaged strands, as hair care products claim.
“A strand of hair is dead tissue, incapable of regeneration once formed,” reminds us Fabiane, a scalp diseases expert. This is why the best way to maintain healthy hair is by having healthy eating habits and eating the proper food, rich in proteins and fatty acids, says the dermatologist. Forty years ago, research studies showed that the lack of such nutrients as iron resulted in hair loss, even among women that did not suffer from anemia, in addition to resulting in dry skin and straw-like hair. More recent studies associated the lack of the lysine amino acid – one of the components of protein, found in red meat, fish and eggs – to hair loss. Long-haired, brunette Fabiane warns us, however, that one must avoid excesses: “Vitamin A in excess increases hair loss and should not be taken without the recommendation of a doctor or a nutritionist.”
Daily use of shampoo does more than eliminate particles of dirt, pollution and scalp sebum that build up on the hair strands. Shampoo is so efficient that it even eliminates tiny particles of the hair strand itself, which results in microscopic damage to the structure, changes the hair color and causes split ends, as evidenced by Inés and by chemist Carla Scanavez.
In experiments conducted at Unicamp’s physics and chemistry lab, Carla decided to find out what daily hair care, such as shampooing, brushing and blow-drying, did to the hair. For the first batch of tests, she placed locks of dark brown hair that had never been exposed to chemical treatment in a bowl of water at 40 degrees Celsius mixed with a small dose of sodium sulphate, a commonly used active ingredient in shampoos. The locks were left in this mixture for 8, 16, 24 and 32 hours. Carla analyzed the strands under an electronic microscope and found that after 16 hours of shampooing – or two months of daily, 15-minute showers – the hair cuticle was full of gaps and cracks; the cuticle, the outer part of the strands, is comprised of 6 to 18 overlapping layers.
The damage to the strands increased when, at a second stage, Carla tried to reproduce a situation similar to the one women face daily. Instead of leaving the sample locks in the mixture, she washed them gently with the shampoo for two minutes, before rinsing them with hot water. She then brushed the wet strands of hair, blow dried them and combed them again. This time, the damage appeared at an earlier stage. “Cuticles start getting damaged after the first 20 repeated movements,” says Carla.
After doing this 120 times, the equivalent to four months of daily shampooing, brushing and blow drying, this hair care regime had practically eliminated the cuticles. It also affected the cortex, the inner portion of the strand that contains 80% of the hair’s keratin, the protein that provides steel-like traction to the hair – the hair strand breaks easily only because of its tiny diameter, which ranges from 50 to 100 micrometers (millionths of a millimeter). One month of washing the hair during the same period of time lightened the hair significantly.
In studies on the effects of hair washing, published in Colloids and Surfaces B, Carla and Inés provided a full explanation on how shampoo detergent affects the state of the strands and the color. The water penetrates the spaces between the cuticles, raises them and dissolves the material deposited between them – normally, dead cells – resulting in small cavities. The detergent in the shampoo speeds up the appearance of spaces in the inner layers of the cuticles and extracts the strand’s natural sebum.
Over time, the cuticles start to detach, which causes the hair’s surface to loose its smooth aspect. This damage makes it easier for water and shampoo to attack the cortex, which results in cavities in the inner part of the strand, by removing the protein and the cell cement that bonds the keratin bundle. In addition to feeling rough to the touch, the strands progressively fade. Two processes are responsible for this: the appearance of the cavities and the destruction of melanin, the protein responsible for hair color – the quantity of melanin determines whether hair is blonde, red, brown or black.
In the case of daily hair care, the cavities in the cuticle and in the cortex of the strand are responsible for hair color changes, due to changes in the optical properties. The greater the amount of cavities in the strand, the more light is reflected from the environment and the less light is absorbed by the melanin. The melanin grains are destroyed at a more advanced stage, which yellows the hair.
People with long hair are more prone to these effects, because their strands of hair are more damaged, especially at the ends. This can be made worse by the way the person washes his or her hair. Rita Wagner, another chemist and a member of Inés’s team, which is comprised mostly of women, submitted brown and blonde hair to two kinds of washing: immersion in shampoo (without rubbing) and rubbing the strands. These two ways of washing hair were repeated at different temperatures, which simulated hot and cold showers. In an initial test, Rita observed that water alone was enough to remove the protein from the hair – this loss was more severe when shampoo was added.
Shampooing the strands of hair was the most harmful action, the researcher wrote in another article published in Colloids and Surfaces B. “The rubbing accounted for 90% of the damage to the cuticle,” says Rita, an effect that increases progressively as the temperature of the water gets warmer. According to Inés, split ends are the first sign of cuticle damage seen by the naked eye; split ends appear one year after hair is consistently shampooed and massaged.
Given that shampoo cleans the strands but damages them to the point that the hair becomes opaque, tangled and brittle when being combed, would the solution be to stop shampooing hair? Fortunately, the solution is not so very radical. Ideally, hair should be shampooed only a few times a week. “The decision on how often to do this depends on personal perception of whether the hair is dirty and needs to be washed,” says Inés. There are no set rules, because the characteristics of the strands and of the scalp vary from one person to another; daily exposure to pollution also differs. “Although there is a very slight difference among the products on the market in terms of their efficacy, shampoo should be the one best adapted to your hair and your scalp,” recommends Inés, who says she does not take any special care of her long, blonde hair.
For people who like to wash their hair frequently, she suggests resorting to baby shampoos, which contain less aggressive detergents. Other recommendations include massaging the strands as little as possible, taking lukewarm showers, towel-drying hair, avoiding too much combing, using a wide-toothed comb, and refraining from using too much shampoo. “One can also use products that reduce any damage from washing,” points out Carla; after years spent on research at Unicamp, she was recently hired by a company from this sector.
Some shampoos include small amounts of silicone in their formulas (dimethicone being one of the best known kinds), a polymer that coats the strands, moisturizing them and making them glossy. “The silicone in the shampoo forms a film over the strands and reduces protein loss through friction,” says Rita. She recently discovered that the medulla, a third component of hair, changes the color and the resistance of the strands.
However, silicone is not entirely harmless: it sticks to the hair strand and is not easily rinsed off. This makes it easier for dirt to build up and demands the use of more detergent the next time. “Many people who believe they have oily hair actually don’t,” says Inés. “The oiliness is caused by the use of an inappropriate shampoo with silicone.”
Conditioners soften the damaging action of shampoos. Conditioners contain fatty-based ingredients and detergents that are different from those in shampoos. They fill in the cavities on the surface of the hair’s cortex and close the cuticles, increasing the capacity of the strands to reflect light – which is why the strands look shinier. Inés also found that conditioners alter hair’s mechanical properties. “This cosmetic makes the strands more homogeneous in terms of the capacity to resist stretching,” she explains. As a result, a smaller number of strands break during combing.
But not even conditioners can remedy one of the most aggressive treatments that Inés has ever seen since she started researching the efficiency of cosmetics on hair in 1983: hair straightening, which people with curly or wavy hair and wanting ramrod-straight hair resort to. Carla applied two kinds of straightening creams available on the market to the sample locks – one cream based on ammonia thioglycolate and the other one containing calcium hydroxide or lithium. She then allowed the creams to act for 20 minutes, the average time of a hair straightening session, and for 60 minutes (three sessions), before analyzing the strands under a microscope.
Even when used in small concentrations, these compounds irreversibly deform the hair’s microscopic structure. Unlike straight hair, which is cylinder shaped, curly hair is flat with natural twists, resembling a winding staircase. Both the thioglycolate and the hydroxide – also used by straight-haired people who want to get curly hair by perming it – destroy the keratin fiber’s bonds, undoing the stands’ microscopic twists. The hair becomes straight and more fragile, like a twisted strand of aluminum that gets stretched. “Cracks and grooves appear, reducing strands’ resistance to straightening by half,” explains Inés.
Something similar happens during thermal straightening. Instead of using creams, this technique involves the use of two heated plates between which a hair lock is placed – this is the modern version of ironing hair. “The hair becomes more opaque and frayed,” says Carla. “To improve the texture, it is necessary to use a lot of conditioner, styling creams and oily compounds, that work like a furniture wax on a scratched tabletop: the grooves are filled in but the damage is not eliminated.”
It is not possible to undo the damage caused by daily hair care and cosmetic treatments on strands; neither is it possible to adequately prevent the changes caused by sun exposure. Chemical engineer Ana Carolina Nogueira exposed samples of white, blonde, red and brown hair to the sun for 91 hours, the equivalent to a one-month vacation on the beach and repeated the test under artificial lighting. She found that the different kinds of ultraviolet radiation (UVA and UVB) damage hair strands in different ways. In a manner which is not yet understood, UVA radiation degrades the melanin, the pigment that determines hair color, which lightens the hair. And the lighter the hair is, the lighter it gets, Ana Carolina described in the Journal of Photochemistry and Photobiology B.
UVB radiation destroys the keratin molecules, weakening them. According to Ana Carolina, the current sun screens do not shield hair completely. “They form a film around the strands. This film contains proteins, which reduces the effects of the UVB rays, but products that reduce the action of UVA rays are still in the development stage,” says the researcher, who currently works for a raw material supplier to the cosmetics industry. Working together, Ana Carolina Lelia Dicelio, from the University of Buenos Aires, identified an unexpected effect of UV rays on white hair: instead of yellowing it, as had been previously believed, sun whitens it. It is infrared radiation (heat) that yellows hair. According to Inés, we have reached a stage that requires that we learn more about how hair works, from a physical and chemical standpoint, in order for industry to be able to manufacture cosmetics that make a difference.
Chemical-physical structure of hair: ethnic differences (04/13066-0); Modality: Regular Research Support Line; Coordinator: Inés Joekes – Unicamp; Investment: R$ 228,934.19 (FAPESP)