Mind Your Membrane: Eight Things You Should Know About Your Skin
Scott LaFee |
November 02, 2015
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- A new
study in the British Journal of Dermatology says the number of moles on a female patient’s right arm is a reliable predictor for the total number of moles on her body. If a woman has 11 or more moles on her right arm, she’s nine times likely to have at least 100 moles on her body. (By some estimates, the average person has 10 to 40 moles.)
Which begs the question: What’s the difference between a mole and a freckle? Most moles are brown or black (though they come in other colors too). They may be flat or raised. They may be present at birth and tend to occur during the first 20 years of life. Freckles vary in color from red to tan to brown. They aren’t present at birth, but develop over time as a result of sun exposure – an effect that happens less often with moles. Most moles and freckles are harmless. A mole can become cancerous (look for changes in size, shape or color). Freckles have no direct health implications, but people who freckle easily (lighter skin) are at increased risk for skin cancer due to overexposure to ultraviolet radiation.
- Your skin is your largest organ. Spread out, it would cover about 22 square feet (on average – about the space of a standard doorway) and weigh roughly eight pounds. You are shedding skin constantly, approximately 600,000 skin cells per hour or about one-and-a-half pounds per year. Your skin renews itself once every 35 days so by the time you’re 70 you’ve cycled through 700 skins and dropped more than 100 pounds of skin cells.
- Skin tags are small flaps of tissue that hang off the skin by a connecting stalk. Their medical name is
acrochorda or fibroepithelial polyps. They’re usually found on the neck, chest, back, armpits, under the breasts or in the groin area. They’re usually the same color as surrounding skin. Women get them more often than men. They’re often triggered by age, weight gain or pregnancy. No one knows what causes them. Some possibilities: recurring friction or a virus.
- Your skin contains roughly 3 million sweat glands, with greatest concentrations on the face, armpits, palms and soles. The average person sweats up to 1.5 gallons per day; up to four gallons if working hard in hot, humid weather.
Acne can develop when hair, sebum (an oily secretion that lubricates and waterproofs the skin) and skin cells clump together into a plug. Bacteria in the plug cause swelling. When the plug begins to disintegrate, a pimple grows. They have many names: Whiteheads are pimples that stay under the surface of the skin. Blackheads rise to the skin’s surface and look black. The black color is not from dirt. Papules are small pink bumps that can be tender. Pustules are pimples red at the bottom with whitish pus on top. Nodules are large, painful, solid pimples deep in the skin. Cysts are deep, painful, pus-filled pimples that can cause scars. It’s estimated 80 percent of all humans experience acne outbreaks at some point in their lives, usually between ages 11 and 30.
- Warts are caused by the
human papilloma virus, of which there are more than 100 types. The viruses are specific to different parts of the body. They are contagious and very common: Almost everyone has a wart at some point in life, though they’re most common among children and young people. Most warts are harmless and disappear on their own after a few weeks or months. “Senile warts” or
seborrheic keratosis typically appear in older people. They are harmless and non-contagious. They are not viral, but rather part of the skin’s aging process.
Birthmarks are distinct regions or patches of differently colored skin, usually obvious at birth. Some fade or disappear with time; others remain static or become larger, darker or thicker. They can be any size, shape, texture and come in many colors, from pink and purple to blue and black. They are almost always harmless and painless. There are multiple causes, including extra pigment in the skin and underlying blood vessels that bunch together or grow abnormally.
- At least 1,000
microbial species, mostly bacterial, reside on human skin with different species preferring different parts of the body. The majority are benign, even helpful, but some are pathogenic and cause skin diseases like rosacea, psoriasis and acne.
Care at UC San Diego Health