GEK2500 Living with Chemistry GEK2500

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GEK2500 Living with Chemistry GEK2500

  1. 1. GEK2500 Living with Chemistry GEK2500 Living with Chemistry Chemistry and Cosmetics (Chemistry and the Attainment of Beauty, and Attractiveness, and Sex Appeal, and ??)
  2. 2. GEK2500 Living with Chemistry What constitute ‘Cosmetics’? • “articles intended to be rubbed, poured, sprinkled, or sprayed on, introduced into, or otherwise applied to the human body or any part thereof, for cleansing, beautifying, promoting attractiveness, or altering the appearance” cosmetics = chemical formulations used for beautifying the human body
  3. 3. GEK2500 Living with Chemistry Drugs or Cosmetics? • Some common cosmetics also alter body functions, may be classified as drugs – e.g. anti-perspirants, sunscreens Skin care Decorative products Odour control Hair applications
  4. 4. GEK2500 Living with Chemistry Skin care • Largest organ in the body, consists of natural polymer and proteins and 10% water • For body temperature regulation, fluid maintenance and disease control Cosmetics - used on outer layer or epidermis - i.e. corneal layer (dead cells) and living tissue underneath Skin treatments - try to soften the corneal layer or add moisture
  5. 5. GEK2500 Living with Chemistry Structure of skin
  6. 6. GEK2500 Living with Chemistry Source: Kline & Co. (C&E News, Nov 6, 2000)
  7. 7. GEK2500 Living with Chemistry Skin softening/moisturizing • Is “skin moisturising” a modern concept? • Began in Near East 3000 years ago - hot desert regions, needed for preventing dryness; mainly use plant oils • Coats skin with mineral oil or petroleum jelly (e.g.Vaseline) • Report: petroleum-jelly based cosmetics can help to repair damaged skin • US$6.4 billion annual sales! (2004) CH3 CH2 CH320 A typical petroleum jelly
  8. 8. GEK2500 Living with Chemistry Some emollients CH3 CH2 CH214 OH Cetyl alcohol (sperm whales or synthesized from plants) C17H35 C O O C27H45 Lanolin (in sheep's wool) • Oil- or fat-based compounds, e.g. lanolin, cetyl alcohol, cocoa butter • melts near body temperature (~37 o C) • Others: beeswax, plant waxes - used to adjust viscosity (an ester)
  9. 9. GEK2500 Living with Chemistry Skin creams • To soften and moisten skin • Oil-in-water emulsions - soap/surfactants added to stabilize the emulsion • Also add vitamins, herbs or plant extracts (e.g. aloe vera) - Effectiveness ? • Many types of creams - cold cream, vanishing cream, etc.
  10. 10. GEK2500 Living with Chemistry Oil-in-water emulsion Bulk water phase Oil phase • Emulsion - dispersion of one immiscible liquid in another, in the form of droplets (Refer to previous lectures on micelles)
  11. 11. GEK2500 Living with Chemistry Do it at home! • Mix 1 part cooking oil with 2 parts water • Shake – what happens? – You should see tiny droplets of oil – Emulsion of oil, but only temporarily • Stop shaking – oily layer reforms (coalesce) • Add some soap or detergent, then shake • Do the drops coalesce? Or emulsion remains? Soap forms coating around each oil droplet
  12. 12. GEK2500 Living with Chemistry A typical cold cream formulation • Cold creams: to clean skin and remove non water-soluble cosmetics Mineral or vegetable oil : 35 - 60% Beeswax (or other wax) : 10 - 15% Lanolin : 5 - 15% Water (perfumed) : 30 -50%
  13. 13. GEK2500 Living with Chemistry Suntan lotions • Suntan lotions do NOT promote tanning!* • Coppertone QT contains dihydroxyacetone (DHA) - reacts with skin (amino acids) to give yellow- brown colouration - but DHA does not protect against sunburn • Most “suntan” lotions now contain sunscreens to prevent UV penetration (can cause skin cancer) * Tanning is body’s way of protecting itself from potential harm by generating a layer of melanin so that part of the radiation is screened out to minimize damage. So, when you get a tan, your skin is already damaged! Although the increased production of melanin is meant to prevent further damage
  14. 14. GEK2500 Living with Chemistry Electromagnetic radiation
  15. 15. GEK2500 Living with Chemistry Heavy mobile use 'damages sperm' (BBC web site, Oct 24, 2006) Experts are calling for further research into the effect of mobiles on fertility Researchers found those men who used a phone for four or more hours a day had fewer sperm and those they had moved less well and were of poorer quality. The study was presented to the American Society for Reproductive Medicine meeting in New Orleans. But a UK expert said it was unlikely the phones were to blame, as they were in use and not near the testes, and it may be being sedentary was the cause. The team from the Cleveland Clinic Foundation in Ohio tested the sperm of 364 men who were being treated at fertility clinics in Mumbai, India with their partners. It was found that the heaviest users, those who used their phones for more than four hours a day had the lowest average sperm counts, at 50 million per millilitre (ml) and the least healthy sperm. Men who used their phones for between two and four hours a day averaged sperm counts of 69 million per ml and had moderately healthy sperm. Those who said they did not use mobile phones at all had the highest average sperm counts, of 86 million per ml, and their sperm was of the highest quality seen. Dr Ashok Agarwal, who led the research, told the New Orleans conference the study did not prove mobiles damaged fertility, but said it showed more research was warranted. "There was a significant decrease in the most important measures of sperm health and that should definitely be reflected in a decrease in fertility, which is seen worldwide. Continued on next slide
  16. 16. GEK2500 Living with Chemistry "People use mobile phones without thinking twice what the consequences might be. "It is just like using a toothbrush, but mobiles could be having a devastating effect on fertility. "It still has to be proved, but it could be having a huge impact because mobiles are so much part of lives." He suggested radiation from mobile phones might harm sperm by damaging DNA, affecting the cells in the testes which produce testosterone or the tubes where sperm is produced. But a British expert cast doubt on the suggested link between mobile phone use and infertility in the men studied. Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: "This is a good study, but I don't think it tackles the issue. "If you're using your phone for four hours a day, presumably it is out of your pocket for longer. "That raises a big question: how is it that testicular damage is supposed to be occur?" Dr Pacey, who is honorary secretary of the British Fertility Society, added: "If you are holding it up to your head to speak a lot, it makes no sense that it is having a direct effect on your testes." He added that people who use phones for longer might be more sedentary, more stressed or eat more junk food, which might be more likely explanations for the link found in the study. September 2008 (Swedish study): Children at risk of future brain cancer if they are heavy users of mobile phones Cf. several past studies
  17. 17. GEK2500 Living with Chemistry Sunscreens • e.g. para-aminobenzoic acid (PABA) – used for years but now not popular because of toxicity and allergic effects (others: cinnamates, benzophenones, PABA esters, salicylates) – blocks out UV-B, but lets UV-A through to tan the skin • e.g. melanin - natural polymer imparts color to skin, level increases after exposure to sun’s rays. Could melanin be used in suntan lotion? NH2 C OH O
  18. 18. GEK2500 Living with Chemistry Sun protection • Should protect from both UV-B (290-320 nm) and UV-A (320-400 nm) • But chemicals in sunscreen can cause problems (toxic, allergens, causing rashes, etc) - perhaps less dangerous than overexposure to UV? • Properties of sunscreens: Sun Protection Factor (SPF) and substantivity (stay-on power) Penetrates underskin more Major cause of sunburn
  19. 19. GEK2500 Living with Chemistry SPF: ratio of time required to tan or burn with the sunscreen compared to the time without it. An SPF of 4 means one must be exposed 4 times as long to tan as much as one would, without the sunscreen 15 is maximum figure – above it, meaningless Substantivity: PABA esters are better than most; octyl-dimethyl-PABA most commonly used. Adding oily lotion will enhance substantivity. How?
  20. 20. GEK2500 Living with Chemistry ST 8/16/02
  21. 21. GEK2500 Living with Chemistry Sun lotions 'are not effective‘ (BBC Sept 29, 2003) Sunscreen lotions may not protect against skin cancer, according to a study by British doctors. The doctors tested three popular brands of sun lotion They have found some leading brands fail to stop the sun's damaging rays from penetrating the skin. Writing in the Journal of Investigative Dermatology, they said further research is needed to see what, if any, creams are effective. The doctors said staying out of the sun or covering up when outside is the best way to protect against skin cancer. Professor Roy Sanders and colleagues at the research charity Raft carried out tests on samples of skin. This skin had been removed from patients with their consent, following a breast reduction operation, for example. The doctors exposed the skin to UVA light at intensities similar to that of sunlight. Exposure to UVA rays is known to cause premature ageing of the skin and increase the chances of skin cancer. They penetrate the skin causing the release of free radicals, which can cause damage to DNA, which can in turn cause cancer. Sunscreen lotions are supposed to stop this from happening. The doctors applied three commonly available high factor sunscreen lotions to their skin samples at the recommended doses. Their tests showed that while the lotions prevented the sun from burning the skin, they did not stop them from penetrating the skin. "They don't seem to offer protection against free radicals," Professor Sanders told BBC News Online. "This is a problem because if people are using these creams on the supposition that they do offer protection then they may be putting themselves at higher risk of skin cancer. "If you use a sunscreen which protects against UVA and take more sun as a result of that, you may be effectively increasing the dose of the UVA and therefore greatly increasing the chances of getting a malignant melanoma. "It's the rise in incidents which is of considerable concern because if it goes on rising, it will become a very serious condition indeed." He said people in Australia were adopting the right approach by encouraging children to cover up with clothing rather than relying on sunscreens when in the sun. "My advice to people is to keep out of the sun or cover up," he said. Dr Mark Birch-Machin, a skin cancer expert at Cancer Research UK, said the findings backed up other studies. He told BBC News Online: "The message from this study is that sunscreens do not provide total protection against skin cancer. They are just part of a toolkit. "They are almost like a last line of defence. People should stick on a hat, a t-shirt and stay in the shade. We shouldn't rely exclusively on sunscreens."
  22. 22. GEK2500 Living with Chemistry Decorative cosmetics • To promote beauty, not health • Lips - lipstick, lip balm • Nails - nail polish, polish remover • Face powder, blushers, etc. • Eyes - eyebrow pencil, mascara, eye shadow, eyeshade etc.
  23. 23. GEK2500 Living with Chemistry
  24. 24. GEK2500 Living with Chemistry Lipstick or lip balm recipe Castor oil, sesame oil, etc.: 45-55% Lanolin or cetyl alcohol: 12-25% Beeswax or carnauba wax: 18-33% Dyes: 4-8% Perfume: trace Balance between: Stiffness (not too runny!) and ease of application (not too stiff), easy removal and substantivity Physical properties versus materials suitability
  25. 25. Boston Globe (Oct, 2007) Parents worried about the dangers of lead in their children's toys, bibs, and homes are about to be confronted with a new potential hazard: their lipstick. The Campaign for Safe Cosmetics is releasing today product test results that found that more than half of 33 brand-name lipsticks tested contained lead. The lead levels in one-third of the lipstick samples, purchased from retailers in four cities, including Boston, exceeded 0.1 parts per million, which is the federal lead limit for candy. The lead levels varied independently of the lipstick's cost, according to the coalition of public health and consumer rights' groups. "There are hazardous levels of lead in lipstick," said Stacy Malkan, a cofounder of the Campaign for Safe Cosmetics. "These tests are a wake-up call to the industry." The lead levels should not concern healthy women without children in their homes, said Joel Tickner, a professor of environmental health at the University of Massachusetts at Lowell. But use of lead-tainted lipstick by pregnant women could lead to lead exposure for the fetus, and lead exposure for children who use lipstick is also a concern, he said. "These levels of lead are not likely to cause poisoning," said Tickner, a specialist on exposure to toxic chemicals. "They are likely to be cumulative to other exposures and can cause subtle neurological effects you can't trace back to a single exposure." The testing, conducted by Bodycote Testing Group laboratory in Santa Fe Springs, Calif., found the highest levels of lead in several samples of L'Oreal and Cover Girl cosmetics. L'Oreal Colour Riche "True Red" lipstick had a lead content of 0.65 parts per million, and a sample of the makeup giant's "Classic Wine" color had a lead content of 0.58 parts per million. Cover Girl's Incredifull Lipcolor "Maximum Red" and ContinuousColor "CherryBrandy" had lead contents of 0.56 and 0.28 parts per million, respectively. In a statement, L'Oreal said it "proudly stands behind" its products.
  26. 26. Continued "Each and every ingredient used in our products has been thoroughly reviewed and tested by our internal safety team made up of toxicologists, clinicians, pharmacists, and physicians," the statement read. "All the brands of the L'Oreal Group are in full compliance with FDA regulations . . . and the requirements for safety in the more than 130 countries in which our products are sold." The findings follow numerous recent nationwide recalls of children's toys and jewelry found to have excessive levels of lead. "There seems to be an almost endless list of products that infant children and pregnant women are exposed to that put them at risk for lead poisoning," said Dr. Sean Palfrey, a pediatrician at Boston Medical Center and medical director of the Boston Lead Poisoning Prevention Program. "If you have a mom who uses a lipstick which has some lead in it and then she gets pregnant, she may be slightly poisoned and can poison her fetus," he said. "Then the baby is born and may have an elevated lead level, which is dangerous." The US Centers for Disease Control and Prevention says there is no safe level of lead exposure for children and has called for eliminating lead hazards in children's environments. But the federal government has not cautioned about lead content in lipstick. Malkan said that lead in lipstick is a valid concern, borne out by the campaign's tests. But she dismissed the cancer scare and a suggestion that consumers can test for lead by scratching lipstick with a gold ring. The Campaign for Safe Cosmetics is calling on manufacturers to reformulate their products to remove lead and is calling on the Food and Drug Administration to more closely regulate the content of cosmetics. But she cautioned that these tests should not be taken as "the definitive word" on lead in lipstick. "It's a tiny percentage of the market in lipstick," she said. "Our test identified a problem in the industry. There's lead in lipstick that doesn't need to be there and shouldn't be there."
  27. 27. GEK2500 Living with Chemistry Nail polish • Used since 3000 B.C. when henna was used for red colour by Egyptians • Becoming a fad again • Ingredients in modern nail polish: – polymer (nylon, nitrocellulose) – solvents (acetone, amyl acetate) – plasticiser (to prevent chipping) – colourants – perfumes • But… covering nails with plastics – healthy? A new class of fingermark detection reagents – from Royal Society of Chemistry website
  28. 28. GEK2500 Living with Chemistry Face powder • To cover blemishes and oily spots, or for colourings • Ingredients: – Absorbent - e.g. chalk (CaCO3) or talc – Astringent - e.g. zinc oxide – Binder (to hold powder to face) – Pigments (depends on type of powder)
  29. 29. GEK2500 Living with Chemistry Eye makeup • Eyebrow pencils – similar ingredients as lipstick – usually not very safe (“do not allow into eyes”, “do not ingest”, etc.) • Mascara: used on eye lashes, added soap for easy removal. Make eyelashes seem longer. How? • Eye shadow: used on skin, can be removed with normal skin washing (soap and water or cold cream)
  30. 30. GEK2500 Living with Chemistry Common colourants/dyes • Titanium dioxide (TiO2) - white • Bismuth oxychloride (BiOCl) - white • Iron oxides (FeOx) - red and yellow • Bronze powder - reddish-yellow • Chromic oxide (Cr2O3) - dark green • Ultramarine (organic) - blue • Manganese salts - violet • Aluminum powder (Al) - silver
  31. 31. Other additives to cosmetics Cosmetics findings: Not too pretty Many popular perfumes, make-ups and deodorants contain phthalates, chemicals that can cause birth defects WASHINGTON - A new face has been put on the notion of suffering for beauty - many popular beauty products contain phthalates, chemicals that can cause birth defects. Three environmental and advocacy groups asked a national laboratory to test 72 products that included popular perfumes, make-up and deodorants. The study, called Not Too Pretty, found phthalates in 52 of the products. More than 10 contained more than one phthalate, a result which surprised researchers because it indicated just how widespread use of the chemicals has become. The study was commissioned by the Environmental Working Group, Coming Clean, and Health Care without Harm. 'Chemicals that can damage the development and future fertility of babies don't belong in products marketed to women,' said Coming Clean campaign coordinator Bryony Schwanm. Phthalate, an industrial chemical used as a plastic softener, has been shown to cause damage to the human reproductive system as well as liver, kidney and lung damage in animals, according to the study released on Wednesday. http://straitstimes.asia1.com.sg/world/story/0,1870,131322,00.html?
  32. 32. More on Phthalates [http://straitstimes.asia1.com.sg/world/story/0,1870,131436,00.html?] PHTHALATES (pronounced thal-eights) are a family of chemical compounds developed in the last century. They look like vegetable oil and have little or no smell. Many personal care products, building materials, clothing, toys, adhesives, inks, pesticides, films, food wraps and food containers contain phthalates. They are most commonly used to make plastics like polyvinyl chloride (PVC) more flexible without sacrificing the plastics' strength or durability. In fact, about 80 per cent of phthalates manufactured today are used in plastics. As they cannot be degraded easily, they have become one of the most abundant pollutants in the environment. In personal-care products, they impart a moisturising film to help dissolve other cosmetic ingredients. Long-term exposure to phthalates can damage the liver, kidney, heart and lungs, according to a study by Health Care without Harm. The study, done on lab animals, suggests that phthalates affects reproduction in the male by causing prostate damage, altering hormone levels and reducing sperm production. In females, phthalates can cause uterine damage, altered hormone levels and decreased fertility. The chemicals can also cause malformations in their young, said the study.
  33. 33. GEK2500 Living with Chemistry
  34. 34. Dissenting view [http://straitstimes.asia1.com.sg/world/story/0,1870,131630,00.html?] COSMETICS: Health alert report 'distorted' facts WASHINGTON - The US chemical industry has dismissed a report claiming that chemicals in cosmetics posed a health risk. The report, released on Wednesday, said that laboratory analysis found the presence of phthalates, industrial chemicals used as a plastic softener, in 52 of 72 beauty products tested. No evidence exists that phthalates are harmful to humans, the report acknowledged, though it cited testing that showed the chemicals may cause defects in animals, notably to the male reproductive organs. Ms Marian Stanley, the senior director of the American Chemistry Council, an industry association, said the report merely rehashed old statistics, as well as misused government data. Ms Stanley, who manages the council's Phthalate Testers Panel, took the report released by the Environmental Working Group, Coming Clean, and Health Care Without Harm to task for 'distorting' the facts in an attempt to scare women away from beauty products. 'There is no evidence of harm to humans from this chemical,' she said. 'DBP (dibutyl phthalate) has been in use in commerce since 1900. That is 102 years of use with no harm reported.' The report suggested that 'surprisingly' high concentrations of phthalates were found in women in a Centres for Disease Control and Prevention (CDC) study conducted in September 2000. 'It is an abuse of CDC figures to claim that,' she said, noting that the report quoted the results of a study of just 289 people, which was described by the CDC itself as 'a grab sample'. Moreover, the highest concentrations of the plastic softener discovered in the women were still well within levels US regulators had concluded that people could ingest daily throughout their life without harm, she added.
  35. 35. More than skin deep - cosmetics go scientific A DNA analysis to customise eye creams, hormone additives: Looking good's no longer about dry or oily skin and it costs (ST July 14, 2003) THE days of hope in a jar are long gone. Today's skin-care companies are marrying science to mass customisation. 'It used to be so simple. Am I dry or not? Do I need moisturiser?' said Ms Beth DiNardo, senior vice-president for global marketing at Clinique, an Estee Lauder brand. Now, she said, customers are being asked to fill in detailed questionnaires. Do they smoke? Are they often stressed? What's their diet like? Want to try even more esoteric science? Let Lab21, a New York company, analyse your DNA from a cheek swab to customise your eye creams and face scrubs. Or, see if your dermatologist stocks one of the new products with human growth hormone, an extract from a baby's foreskin. The personal and scientific approach comes at a price. Mass-market brands, like Olay or Neutrogena, that rarely topped US$10 (S$17.50) now command upward of US$20 for products with scientific-sounding ingredients. A 56g jar of Re Vive carries a US$375 price tag. Dermapolish costs US$125 for an eight-week supply. Critics of these scientifically based products are easy to find. 'If the things you see on the labels had the effects they claimed, they would have to go through the US Food and Drug Administration,' said Dr Irwin Freedberg, head of the dermatology department at the New York University School of Medicine. Dr Leslie Baumann, chief of cosmetic dermatology at the University of Miami School of Medicine, is equally scornful. 'The old cosmetic advertisements used to just say: Our product will make you more beautiful and keep your husband from cheating. Now, they talk about some high-tech sounding protein that slows the ageing process,' she said. 'But, very few ingredients do the things they say they do, and I'm not sure all of them are safe.‘
  36. 36. In fact, companies have carefully steered clear of ingredients, dosages or claims that could raise a red flag to regulators. They note that many of their ingredients made their debut in medical journals, and that they have published their own results in cosmetics journals. For example, numerous studies show that penta-peptides and copper peptides heal wounds, they note, so, of course, they can 'heal' ageing skin. Genomic research can spot all kinds of predispositions - so why not a predisposition to react to a skin cream or pollutant? If microcrystals work when dermatologists use them to abrade skin, why shouldn't they work in Dermapolish? If Retin A, a powerful vitamin A derivative, is prescribed for combating wrinkles, then products replete with retinols and retinoids derived from vitamin A or from Retin A should work as well. Drug companies are pumping research dollars into aesthetic dermatology. For example, last year, Pfizer formed Anaderm (Greek for 'new skin') to develop prescription creams that could fight ageing or oily skin, and abnormal hair loss or growth. Dr Arthur P. Bertolino, Anaderm's clinical exploratory head, predicts the products will be blockbusters. 'We're talking hundreds of millions of dollars, maybe over a billion, for each,' he said. The line between doctor's offices and cosmetics counters is blurring as more dermatologists offer their own emollients and creams. The plethora of molecules du jour was probably inevitable. More than a decade ago, companies began putting alpha-hydroxy acids, retinols and retinoids, vitamins C and E, and all kinds of other scientific ingredients into what used to be mundane creams. Their sales shot up. In late 1993, for example, Unilever's Ponds brand offered its first alpha-hydroxy product, and its face cream sales doubled in a year. Avon Products, which had introduced alpha-hydroxy products even earlier, also had a huge increase in sales. 'Since then, everyone has been looking for the next magic bullet,' said Mr Alex Znaiden, senior vice-president for research and development at Unilever North America. -- New York Times
  37. 37. GEK2500 Living with Chemistry
  38. 38. GEK2500 Living with Chemistry Odour control • Perspiration - normal body function to remove waste and maintain temperature • Sweat contains NaCl salt, fatty acids (e.g. caproic acid), amines and sulfur compounds — smelly stuff • Huge market in natural odour prevention • Washing with soaps, or use other means to mask, change or prevent the odour
  39. 39. GEK2500 Living with Chemistry Deodorants and Antiperspirants • Deodorants: mask or absorb body odour – powders: talc or chalk as absorbent – also add oxidants to oxidize fatty acids into less odorous compounds • Antiperspirants: similar to deodorants but add astringent to prevent formation of sweat, e.g. aluminium chlorohydrate* – constricts sweat gland pores, so no perspiration forms • Add perfumes for enhanced effect • Can also buy mineral salts (in stick form) to apply to underarm and elsewhere – how does this prevent odour formation? Will it prevent perspiration? * What’s the concern over aluminium chlorohydrate?
  40. 40. GEK2500 Living with Chemistry Perfume, cologne and aftershaves Perfume Cologne Aftershave Fragrance 10-25% 1-3% <1% Fixative 2-5% 0% 0% Ethanol 70-88% 77-84% 59% Water nil 15-20% 40% • fragrance - pleasant smelling esters, alcohols, aldehydes, ketones • fixatives- prevent rapid evaporation of aroma
  41. 41. GEK2500 Living with Chemistry Hair Chemistry • Hair - mostly protein, e.g. keratin • Hair keratin - made up of 16-18 % cysteine (containing an -SH group) • Cysteine forms S-S (disulfide) crosslinks between different protein chains in hair -provides durability and shape • Hair is less flexible and less elastic than skin because of these crosslinks (skin keratin ~2-4% cysteine)
  42. 42. GEK2500 Living with Chemistry Hair sprays • ~ 4% polymer in a volatile solvent • Ingredients: – polymer (holds hair in place) e.g. poly(vinyl pyrrolidone) – plasticiser (makes polymer pliable, soft) – silicone oil (adds sheen) • use pump-type bottle or non-CFC formulations (ozone problem)
  43. 43. GEK2500 Living with Chemistry Hair colour • Hair has 4 pigments within protein chains: Melanin (brown-black, major) Phaeomelanin (red pigment, major) Oxymelanin (yellow pigment, minor) Brown melanin (brown, minor) • All are polymers, also found in skin and eyes • A person’s hair colour - relative proportions of these 4 pigments • 90% of world’s population has dark or black hair
  44. 44. GEK2500 Living with Chemistry Hair colour and bleaching • White/grey hair - little or no pigment • Bleaching - an oxidation-reduction reaction to convert the pigments to colourless forms • e.g. hydrogen peroxide (H2O2) • also makes hair more brittle because protein structure is affected (→ lower molecular weight) Melanin + H2O2 Degraded melanin pH > 9
  45. 45. GEK2500 Living with Chemistry The pH scale • [H+ ] represents the concentration of H+ ions in the solution pH = - log [H+ ] • at [H+ ] = 10-4 (high concentration of H+ ) pH = 4 (acidic solution) • at [H+ ] = 10-11 (low concentration of H+ ) pH = 11 (basic solution) • For neutral solution, pH = 7
  46. 46. Hair dyes • Metallic dyes, e.g. lead acetate – black PbS is formed and adheres to the hair (Grecian Formula) • Temporary dyes – only coat the hair surface, easily removed (FD&C Blue No. 1); small dye molecules can also migrate in and out of hair • Semipermanent dyes, e.g. para- phenylenediamine (two-step process) – Primary and secondary intermediates penetrate into the hair fibers; Hydrogen peroxide (H2O2) oxidizes the primary one. – the oxidized form reacts with the secondary intermediate to form the colour. The dye molecule is entrapped within the fibers. – Several types of intermediates: one such intermediate has been known to cause cancer in animals (2,4-diaminoanisole, or 4-methoxy-m-phenylenediamine, MMPD) melanin no melanin no dye penetration, on surface only dye penetration to voids once occupied by melanin white or grey hair, no melanin Black dye; For blonde - Derivative is para- aminodiphenylaminesulfonic acid THINK! H2O2 is a bleach – why do we need it if we wish to add colour to hair, and not reduce colour of dark hair?
  47. 47. GEK2500 Living with Chemistry Read more: http://europa.eu.int/rapid/pressReleasesAction.do?reference=IP/06/1047&format=HTML&aged =0&language=EN&guiLanguage=en Are hair dyes safe to use? (from the Alchemist Newsletter, July 26,2006) Dyed hair today, gone tomorrow Long-term use of certain hair dyes has an increased risk of bladder cancer, according to European Commission scientists. As such, 22 hair dye chemicals are to be banned across the European Union. There is conflicting evidence that suggests such a stance should not be taken, but the Commission nevertheless insists the ban will improve consumer safety. The Commission says that safety data have not been submitted for these 22 chemicals, which include 4-hydroxyindole, 2,3-naphthalenediol, Acid Orange 24, and 3,4-diaminobenzoic acid. The ban is likely to have a rapid commercial impact as the hair dye market in the European Union was 2.6 billion euros (about US$3.3 billion) in 2004 which accounts for some 8% of the value of output of the cosmetics industry in Europe. European Commission Vice-President Günter Verheugen, responsible for enterprise and industry policy, said: "Substances for which there is no proof that they are safe will disappear from the market. Our high safety standards do not only protect EU consumers, they also give legal certainty to European cosmetics industry." Read more: http://europa.eu.int/rapid/pressReleasesAction.do?reference=IP/06/1047&format=HTML&aged =0&language=EN&guiLanguage=en
  48. 48. GEK2500 Living with Chemistry Permanents and straighteners • Permanent waves - make straight hair curly • Straighteners - make wavy hair straight Same chemistry – oxidation/reduction • Waving and straightening: S-S linkages between hair fibres are broken (reduction), hair is reshaped, then cross-linkages restored (oxidation) Reducing agent - thioglycolic acid Oxidizing agent - hydrogen peroxide
  49. 49. GEK2500 Living with Chemistry Waving and straightening
  50. 50. GEK2500 Living with Chemistry -S-S- reduced to -SH HS- oxidised back to -S-S-
  51. 51. Hair sprays? - Resins that form sticky film on hair - Polyvinylpyrrolidene (PVP) – polymer - To get shiny hair (sheen) – use as yet more chemical: silicone polymers Hair removers? - Depilatories - Alkaline chemical (calcium thioglycolate) in lotion or cream that destroys peptide linkages - Will damage skin? Why or why not?
  52. 52. GEK2500 Living with Chemistry But what if you don’t have any hair to work on? Hair restorers: e.g. Minoxidil, which acts by dilating blood vessels. Hair will grow where there are functioning follicles. Approved by FDA in 1996.
  53. 53. GEK2500 Living with Chemistry What if you wish to remove hair? Depilatories: Contain sulfur compounds that are formulated into cream or lotion. Strongly basic, will destroy peptide bonds in hair so they can be washed off. Any side effects? Can damage skin
  54. 54. GEK2500 Living with Chemistry Cosmetics Drugs? For Beautifying? Skin care Skin - organ Softener/moisturiser Skin cream Suntan lotion Sunscreen Decorative cosmetics Lips Nails Eyes Face Colourants Antiodour, antiperspirant, aftershave, perfumes, colognes Hair Chemistry

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