Thursday, October 20, 2011

Sensitive Skin Part II: Dry Skin


You know it’s coming. Winter. If you live in the more Northerly latitudes, especially away from the oceans, this means cold, dry air, indoor heating and generally a desiccated time for your skin and hair. Itchy skin, rough, cracking hands, chapped lips, windburn…
©Science-y Hair Blog 2013
Dry, rough skin on feet
This is going to be similar to the “sensitive skin” post because dry skin is sensitive skin – it’s more vulnerable to tearing and injury, loses more water, you want to scratch the itch which damages skin.
©Science-y Hair Blog 2013
The ability to respond to dry environments is where skin and hair diverge. Skin can try to respond to this but hair cannot. The stratum corneum (upper layer of skin) contains “Natural Moisturizing Factor” a blend of lipids and humectants (fats and water-attracting chemicals) which attract and hold water - the key ingredient that keeps skin soft, flexible and moist (as opposed to cracking, peeling and flaking). When the air gets dry, your skin starts breaking down proteins more rapidly than when the air is humid. As this happens, more Natural Moisturizing Factor is the result. Hyaluronic acids, lactic acids and other hydrophilic or water-attracting compounds released stimulate ceramide (lipid) synthesis to keep your skin acting as a healthy, moist, flexible barrier. Skin reacts to dry air by trying to improve its ability to hold water. And the amazing thing is that this occurs in cells which are no longer living.©Science-y Hair Blog 2013

Hair is made of proteins (which strongly attract water) and also hosts amino acids and lipids which hold water in the fiber. The oils from the scalp (sebum) are also meant to keep water in the hair. But hair cannot alter its composition in response to dry air.
Dry skin, close up



About that sebum: Skin has a layer of sebum on the very top of your skin cells – cholesterol, glycerides, free fatty acids, wax esters, squalene, and cholesterol esters and lots of bacteria. This layer of hydrophobic (water-repelling) sebum protects skin from dehydration (and can spread through hair to prevent dehydration) and maintain a pH of slight acidity, protecting your skin from pathogenic or disease-causing bacterial and fungal overgrowth. You want to keep this on your skin! Soap or very lathery and foamy liquid detergents (antibacterial detergents/soaps are big offenders) strip away this protective layer and then your skin is as vulnerable as untreated wood in the outdoors.
©Science-y Hair Blog 2013
Skin: Avoid washing your skin with soap or liquid detergents as much as possible. Keep the lather on your armpits, groin, feet, and face (and anyplace else that gets dirty or smelly). Washing (rinsing, really) with water alone increases trans-epidermal water loss (water moves from skin to air) and raises the pH of skin but washing with soap has a greater effect on trans-epidermal water loss and irritation of skin.
Keep showers short and not hot. If you simply must have a hot shower or bath on those cold days when your body aches from shoveling snow and shivering in the cold and wind, rub a little oil on your skin before getting into the shower.
Choose moisturizing soaps or liquid detergents and body washes which are not antibacterial and are meant for sensitive or dry skin – and use them sparingly.
Apply a generous amount of lotion right after showering – towel your skin dry, apply skin lotion, let it “soak in” for a couple minutes before dressing. This makes use of the moisture absorbed by your skin during the shower – lotion should seal this moisture in.
Choose a thick, rich lotion. Avoid fragrances, bright colors and exfoliating ingredients.
Avoid wearing any clothing which feels itchy or rough, this will irritate your skin, which leads to further barrier disruption and dryness.©Science-y Hair Blog 2013

Protect skin with long socks (to fight the up-the-trousers-leg draft), warm clothes, long sleeves, gloves and mittens, a hat and even a light scarf over your face. Human facial skin exposed to cold air and wind is in a constant state of irritation. The best defense is protection – if a scarf over your face is out of the question, use plenty of lotion.©Science-y Hair Blog 2013

Hair: As for skin, less-frequent washing is best, you want to keep the sebum and avoid dehydrating the hair fibers. Most of the ingredients listed that are good to look for in skin lotion are good for hair. Some people will need more emollients than others for their hair, but in general, humectants combined with emollients and emulsifiers are ideal for hair care. When the humidity drops very low, one may want to avoid humectants in hair care products because the hair cannot adapt like the skin can to dry air, so additional humectants cannot moisturize as well (but still may do some good). Extremely dry air will not allow the humectants to hold water and can probably compete with the humectants for moisture.
©Science-y Hair Blog 2013
Protect hair with a loose but warm hat. You can line the interior of a hat with a silky fabric to prevent rubbing on the hair and skin. This simple sewing task (it doesn’t have to look good) makes a huge difference in how your hair looks post-hat removal, in reducing hair breakage and preventing friction on the scalp and forehead. Hats keep the cold air off your hair and scalp, and hold some humidity in, preventing dehydration.
©Science-y Hair Blog 2013
Know your ingredients: The top ingredients listed on a product are the most abundant. You want to look for these types of ingredients in the top 6-8 on the list. Water is usually one of the top ingredients. Lotions have more water than creams and ointments (thick and greasy) usually have no water.
©Science-y Hair Blog 2013
Emollients/occlusives – hydrophobic or water-repelling ingredients to prevent loss of water from your skin and hair. “Repelling” in this case means they’re not only keeping water out, but they’re preventing the water in your skin from escaping:
Oils (vegetable/seed/plant oils and mineral oil)
Petrolatum
Dimethicone and silicones
Triglycerides
Squalene
Isopropyl Palmitate (can irritate skin or cause acne breakouts)
Cetyl esters
Alkyl esters
Jojoba esters
Butters (shea, cocoa, avocado)
Waxes (jojoba, beeswax)
Cholesterol
Ceramides

Humectants: Choose skin creams and lotions with humectants to attract and retain water from deeper skin layers and from water-moistened skin including:
Glycerin
Urea
Sodium lactate 
Hyaluronic acid
Sodium PCA
Amino acids 
Propylene glycol (can be irritating to sensitive skin!)
Oatmeal (colloidal)
Aloe vera
Sorbitol
Glycine betaine
Caprylyl glycol
Panthenol (humectant-like, skin-soothing)
Proteins
©Science-y Hair Blog 2013

Emollient thickeners work with emulsifiers to preventing separation and adding a creamy feel, allowing lotions and creams to glide over your skin. These can also leave a soft, silky feeling on skin and hair rather than an oily feel or tacky “drag”:
Cetyl alcohol (the definition of alcohol based on vegetable fats, the “alcohol” refers to the chemical structure, these do not evaporate quickly and dry the skin like ethyl or isopropyl alcohol)
Cetearyl alcohol
Stearic acid
Stearyl alcohol
©Science-y Hair Blog 2013
Cationic surfactants are “conditioners” with positive charges to bond to skin and hair, leaving a coating of “conditioning” bonded to skin and hair, as well as emulsifying and adding glide to products:
Cetrimonium chloride
Behentrimonium chloride
Behentrimonium methosulfate
Cetrimonium bromide
Decetyldimonium chloride
Stearalkonium chloride

Exfoliation: it seems counter-intuitive, but a little exfoliation on dry skin can be a good thing. When your skin gets ashy or dull-looking, feels rough, itchy and flaky and lotion is not doing enough, mix about half sugar and half vegetable oil (or mineral oil if vegetable oil makes your skin itchy). Gently massage this on the affected areas. Wash with a gentle detergent in the shower and use skin lotion afterwards. Your skin will feel soft for days. Do not use this scrub on injured or damaged skin.
©Science-y Hair Blog 2013
Humidify!
In your house or apartment, keep the air humidified in cold, dry climates. Up to 45% humidity is ideal, but a reasonable goal is 30-35%. Greater than 45% humidity encourages mold and dust mite growth which is undesirable if you have allergies or asthma.
You can use a humidifier in your living room and bedroom to prevent itchy, dry skin and brittle hair. Take the time to clean them frequently – daily if you have hard water - they’ll last longer, leak less, and are easier to clean if cleaned often.
You can also buy a clothes drying rack and hang some or all of your laundry on it to not only add moisture to the air, but save money on energy and help your clothes last longer. If you hate the “crunchy laundry” feeling – toss them in the dryer with no heat for a few minutes when the clothes are dry to soften them. You can string a clothes line in your house or use a piece of very long dowel to hang them on. It's an inexpensive way to humidify.
Clothes drying rack
Clothes drying rack

©Science-y Hair Blog 2013
Coming soon: How to line a warm hat with silky fabric to prevent hair breakage and skin irritation!



Sources:
Journal of Investigative Dermatology 2008 Water Distribution and Natural Moisturizer Factor Content in Human Skin Equivalents Are Regulated by Environmental Relative Humidity. Joke A Bouwstra, H Wouter W Groenink, Joop A Kempenaar, Stefan G Romeijn, Maria Ponec 
Journal of Wound Ostomy Continence Nursing. 2008 Jan-Feb;35(1):84-90.
The effect of washing and drying practices on skin barrier function. Voegeli D.
ICRP Publication 89: Basic Anatomical and Physiological Data for Use in Radiological Protection: Reference Values. Jack Valentin, ICRP

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