The skin Chien-Ming Li MD, Ph.D 1. Skin is the human body s largest organ. 2. The average skin, when stretched out, is 2 square meters. 3. Skin accounts for around 15% of your body weight. 4. There are two types of skin: hairy and glabrous. 5. The average person has about 300 million skin cells. A single square inch of skin has 19 million cells and up to 300 sweat glands. 6. Your skin has three layers: 1) epidermis-dead and waterproof, 2) dermis-hair and sweat glands, and 3) subcutis-fat, blood vessels. 7. Every inch of your skin has an exact stretchiness and strength for its location; skin on knockles is different from the ones on belly. 8. The thinnest skin is found on your eyelids: 0.02 mm thick. 9. The thickest skin is found on your feet: 1.4 mm deep. 10. Scar tissue lacks hair and sweat glands. 11. A body hair will grow from 2-6 years. 12. You lose around 20-100 hairs a day. 13. Hair is made from a protein called keratin. 14. Keratin also forms the dead outer layer of human skin and fingernails. 15. Every hair has a small muscle, the pili. This allows your hair to be raised when cold or in a heightened emotional state. 16. Over 50% of the dust in your home is actually dead skin. 17. Lipids are natural fats that keep the outer layer moist and healthy. 18. Every minute, your skin sheds over 30,000 dead cells. 19. Your skin has its own bacteria microbiome of over 1000 species and 1T individual bacteria. 20. Sweat is odorless; it s the bacteria that make body odor. 21. The glands that produce wax in your ears are specialized sweat glands. 22. On average, 14 species of fungi live between your toes. 23. Skin color is the result of a protein called melanin; melanocytes produce and distribute melanin. 24. Human skin comes in a very wide range of colors. 25. Around 7% of skin cells are melanocytes. 26. There are two types of melanin: 1) pheomelanin-yellow to red, and 2) eumelanin-dark brown to black. 27. Everyone has the same number of melanocytes; skin color is a due to their activity, not quantity. 28. One in 110,000 people have albinism: a lack of melanocytes.
29. Melanin is also responsible for eye color. 30. It takes up to 6 months for babies to develop their permanent skin color. 31. Acne is caused by an over production of cells that line the sweat glands. 32. Sometimes, babies get acne in the first few weeks of life. 33. Four out of five teenagers get some form of acne. 34. One in 20 adult women suffers from acne. 35. One in 100 adult men suffers from acne. 36. Boils are caused by the Staphylococcus bacteria; it enters through a tiny cut and travels down to the hair follicle. 37. For healthy skin you need: 1) vitamin A-treats sun damage and cellulitis, 2) vit D-reduces spots and growths, 3) vit C-antioxidant, regenerates vit E and provides sun protection, 4) vit E-antioxidant, protects against sun damage and aging. 38. Skin at least has 5 different types of receptors responding to pain and touch. 39. Skin can form additional thickness and toughness: a callus, if exposed to repeated friction or pressure. 40. The skin renews itself every 28 days. 41. Wrinkle: furrow or crease in the skin due to aging or frowning 42. Nevi: flat or raised, hyperpigmented area on the skin 43. Keloid: excessive collagen formation in the process of wound healing 44. Skin cancer: melanoma, basal cell carcinoma, squamous cell carcinoma 45. Sensory receptors of skin: 1) baroreceptor, 2) chemoreceptor, 3) electromagnetic radiation receptor, 4) hydroreceptor, 5) mechanoreceptor, 6) nociceptor, 7) osmoreceptor, 8) proprioceptor, 9) thermoreceptor 46. Aging: 1) baldness, 2) absence of eyelashes, 3) absence of eyebrows, 4) swollen veins, 5) beak-shaped nose, 6) shrunken chin, 7) age spots, 8) dryness
47. Skin care 1. Skin-care misconceptions, fallacies, and flat-out wishful thinking are as plentiful as cleansers in a drugstore. Some are long-held beliefs passed down for generations, such as the notion that squeaky-clean is a virtue. Others are convincing for their grounding in modern technology. But with help from doctors (and years of research), the truth has at last been separated from the eh, not so much. 2. 3. 4. 5. Rumor: Squeaky-Clean Skin Is, Well, Squeaky-Clean 6. Reality: Overzealous face washing, whether more than twice a day or with products that leave your skin as tight as a drum, can actually cause damage, says Cheryl Karcher, a dermatologist in New York City. The water-cleanser combo can strip skin of its natural oils and compromise its barrier, which can set you up for irritation and dehydration, she says. Therefore you should avoid cleansers that contain harsh surfactants, which rid skin of too much oil and leave it so dry that it feels taut and might just squeak if you dragged a
finger across it. Some common surfactants include sodium lauryl sulfate (SLS), sodium lauryl ether sulfate (SLES), and ammonium lauryl sulfate (ALS). Instead of these, look for gentler cleaning agents, which may be glucose-based or derived from coconut oil. They can take off makeup but still maintain skin s suppleness. These include coco betaine, cocamidopropyl betaine, coco glucoside, decyl glucoside, and sucrose laurate. And if you use cleanser at night, a quick splash of cool water alone will suffice in the morning. (However, if you re a morning gym-goer, you ll need to cleanse again, since sweat can clog pores.) For midday greasiness, try oil-blotting papers or waterless cleansing wipes. 7. 8. Rumor: Botox Can Prevent Wrinkles 9. Reality: Theoretically, yes. But no long-term studies support this claim. If you relax the muscles that continually contract, you ll be less apt to see creases over time, says Fredric Brandt, a cosmetic dermatologist with practices in New York City and Coral Gables, Florida. But other strategies, like using sunscreen and keeping up proper skin care, are more reliable and certainly less expensive options for fending off wrinkles. If you still feel compelled to go under the needle, Los Angeles and New York City dermatologist Karyn Grossman advises beginning Botox treatments no earlier than when fine lines first appear, generally in your 30s. 10. 11. Rumor: Oily Skin Doesn t Wrinkle as Much as Dry Skin 12. Reality: The research isn t definitive, but this supposition seems to make sense. Oily skin may fend off wrinkles more easily because it tends to be thicker, which affords more natural protection against sun damage, says Brandt. Ruthie Harper, an internist in Austin, Texas, ties the phenomenon to hormones. Women with oily skin may have higher testosterone levels, she says, which can help protect against diminished collagen levels and, in turn, wrinkles. But this is not to say that oil-prone skin doesn t ever look old. And factors such as sun exposure and smoking speed up the aging process and cause wrinkles, regardless of skin type. 13. 14. 15. Rumor: Junk Food Causes Acne 16. Reality: So far, no studies have shown a direct correlation between junk food and breakouts or acne, says David Bank, a dermatologist in Mount Kisco, New York. And most of the other dermatologists interviewed for this story
agree with Bank. However, associations have recently been made between the consumption of high-glycemic foods (typically foods that contain refined carbohydrates) and breakouts among people who are acne-prone. Why? Inflammation is known to aggravate acne, and high-glycemic foods (such as white rice, sweets, and sugary drinks) can raise blood sugar and insulin levels quickly, leading to inflammation. And though dark chocolate may in fact offer multiple health benefits, milk chocolate is being called into question as a possible cause of acne. In a recent study published in the Journal of the American Academy of Dermatology, Italian researchers found that drinking more than three glasses of full-fat or skim milk a week could increase the risk of moderate to severe acne in those who are predisposed to flare-ups. The key, says Harper, is to limit these possible triggers and balance them out with foods and beverages that contain anti-inflammatory benefits, such as green tea, broccoli, and fish rich in omega-3 fatty acids, which have been linked with a 32 percent decreased risk of acne when eaten at least once a week. 17. 18. Rumor: For Best Results, Use Skin-Care Products From the Same Line 19. Reality: You don t need to, says Bank: Generally this is just clever marketing. There are, however, certain ingredients that companies pepper throughout a certain line that are especially efficacious when used together. For example, you may find a blemish kit that contains an anti-acne cleanser with salicylic acid to help unclog pores and a gel treatment with glycolic acid to prevent future pimples. If you re trying to address a specific problem, like acne-prone skin or dark spots, this prepackaged approach may make it easier, says Grossman. 20. 21. Rumor: You Can Get Rid of Cellulite 22. Reality: No cellulite fix is permanent, says Howard Sobel, a dermatologist in New York City. Some treatments might minimize the look of cellulite, such as creams that contain aminophylline (which helps break down fat cells) and massaging devices that iron out fat cells somewhat so that they don t appear as pronounced. But these remedies last, at best, a few months. Even liposuction, which removes excess deep-fat deposits, doesn t necessarily improve the surface of the skin to the degree where the dimpled effect is invisible, says Sobel. There is, however, a ray of hope: Cellulaze, a laser treatment that cuts the little vertical bands under the skin that are attributed to the dimpling effect and smooths them out. The treatment recently received clearance from the U.S. Food and Drug Administration (FDA) for treating cellulite long-term, says
Barry DiBernardo, a plastic surgeon in Montclair, New Jersey, and the lead clinical investigator of the FDA trials of Cellulaze. But it doesn t come cheap. The cost can run from $3,000 to $8,000 for the one session that you ll need. 23. 24. Rumor: The Higher the SPF, the Longer You Can Stay in the Sun 25. Reality: No, no, no. SPF isn t an indication of how long a product protects you from the sun s blistering, cancer-causing UVB rays but how well it does so. What s more, SPF doesn t refer to the product s ability to shield you from UVA rays, which, in addition to causing skin cancer, have been linked to causing wrinkles. Your best bet: sunscreen labeled broad-spectrum (which means it covers both UVA and UVB rays) with an SPF of 30. Why? While an SPF of 15 screens out only about 93 percent of UVB light, an SPF of 30 filters out 97 percent and those any higher don t offer much more benefit. Remember: Any sunscreen will be effective only if it s reapplied at least every two hours; use at least a teaspoon of it on your face and a shot-glass size amount on your body. 26. 27. 28. Rumor: After a While, Your Skin Gets Used to Products 29. Reality: It depends on the active ingredients, says Grossman: Your skin does acclimate to vitamin A derivatives, such as retinols, and prescription retinoids, like Retin A, Differin, and Tazorac. (For this reason, Grossman typically starts her patients on milder forms of the derivatives, then increases the intensity incrementally.) But this is not the case with antioxidants, moisturizers, and peptide products. (Peptides are amino acid chains that are increasingly being added to creams and serums because they are thought to stimulate collagen production.) Still, improvements might plateau because you ve reached a cream s capacity for change. If so, you may need to choose a stronger product for continued progress. Try different active ingredients, or switch to prescription products. 30. 31. Rumor: Facial Exercises Keep Skin Taut 32. Reality: Alas, no. The muscle contractions used in facial exercises can actually contribute to wrinkling, says Brandt. Think of your face as a piece of paper that s being folded over and over again in the same spot. After a while, that area becomes permanently etched. And if you re hoping that facial exercises can fill out hollows caused by sagging, here s some bad news: There s no concrete evidence of plumping benefits, either, says Bank.
Volume loss is caused by a decrease in collagen, elastin, and fat none of which can be replaced by exercise. 33. 34. Rumor: All Skin Damage Occurs by Age 18 35. Reality: Not so. UV-ravaged skin will turn from bad to worse if you expose it to sun after age 18, which may ultimately lead to skin cancer. So shielding skin diligently with daily sunscreen use is crucial. You can liven up the look of already damaged skin by improving its tone and smoothing fine lines. Exfoliate about three times a week with a gentle gritty cleanser or with one containing a chemical exfoliant, such as an alpha hydroxy acid. (Experiment to find out which one your skin will tolerate best.) Next, apply an antioxidant-rich broad-spectrum moisturizer with an SPF of 30 or higher every day, and use a brightening retinol product every night, says Brandt.