Dermatologist Explains: What Causes Dry Skin?

Cynthia Bailey, MD|January 21, 2012

Your skin becomes dry when it loses both water and it’s natural skin oils.  In the lab we see big differences between dry skin and hydrated skin in both the composition of the chemistry of the skin layers and the way they look structurally when examine under a microscope.  The structural and chemical characteristics of dry skin translates to skin that’s also more vulnerable. We call this vulnerability of dry skin an impaired barrier function.  For you, dry skin means that:

  • your body’s water, which is normally present in your skin, is escaping more easily (called transepidermal water loss).
  • soaps and solvents are better able to penetrate deeply into your skin and pull out your natural skin oils.

You can see why the problem compounds, getting worse and worse, and you’ve undoubtedly experienced it.  The most common example is chapped hands.  Once your hands are chapped they get worse and worse every time you take them outside into harsh weather or do the dishes without gloves again.  Your skin becomes rougher, dryer, itchier, starts to crack, hurts, becomes rougher and dryer etc… What’s happening is that your impaired barrier can’t stand up to the usual insults of weather and soaps.  Harsh weather ‘pulls’ water out of your skin into the dehumidified wind.  Soaps seep into chapped skin  ‘cleaning-out’ more of your skin’s natural oils.  Unless you intervene, your skin gets drier and drier and its barrier weaker and weaker. The intervention is actually simple – stop exposing the skin to situations that decrease its water and oil content, and instead do something to increase these important components of healthy skin.

Dermatologist’s advice to heal dry skin:

1.  For starters, wear gloves, clothing or facial mufflers to protect skin from harsh weather so that water isn’t ‘pulled’ out so rapidly. 2.  Increase the relative humidity of the air that you expose your skin to by adding an indoor humidifier. (Or, hello Hawaii!). 3.  Minimize the exposure of your skin to harsh solvents and soaps that ‘clean out’ the oils you need for a healthy skin barrier.  This means wearing protective gloves when you must come into contact with these things, such as when doing the dishes. 4. Use only gentle cleansers when you wash your skin because skin cleansing also ‘cleans out’ your natural skin oils.  Have only gentle cleansers handy at your sinks and in the shower.  Rinse them off well too because soap residue can irritate skin and even gentle soaps will pull oils out of your skin given hours of opportunity. For chapped dry skin care I recommend only skin cleansers with a high glycerin content and no sodium laurel sulfate foaming agents.  Safe options include pure glycerin bar soaps and naturally made bar soaps that retain their natural glycerin.  Whole Foods 365 brand glycerin bar soap is a deal at about $2 and is a great all-purpose skin cleanser.  Other commercially available liquid cleansers that meet this criteria include Toleriane Cleanser, which is my 'go-to' cleanser for cleansing dry sensitive facial skin. best facial dry skin cleanser 5.  Apply a high quality skin moisturizer that’s rich in oil immediately after washing or bathing skin.  This will add oil back and help to trap water. Water enters your skin during water exposure and oils prevent its evaporation by sealing it in.  The oils will also seep into your skin to replace your lost natural oils. Find a product you like and use it as often as possible. Most commercial moisturizers have petrolatum or mineral oil as their therapeutic oil ingredients and many scientific studies over the years have proven the effectiveness of these oils for repairing skin barrier impairment.  There are also products with natural oils that work beautifully too such as almond oil, shea butter, olive oil, jojoba oil etc.  Other moisturizing oil ingredients that can be helpful are ceramides which more closely resemble your skin’s natural oils and are important for healthy skin barrier. Moisturizers that also contain humectants (water binders) are even more effective than those based solely on their oil content.  Look for humectant ingredients such as

  • urea,
  • the alpha hydroxy acids called lactic acid and glycolic acid,
  • glycerin
  • hyaluronic acid.

These humectants boost skin water content by binding water in the skin, thus preventing it’s loss.  Urea and alpha hydroxy acids however can irritate severely chapped skin and you need to heal your chapped skin before you start using them. It's possible to find products that specifically heal and protect dry, chapped, barrier impaired skin and that are not heavy or oily.  For example, my favorite humectant containing hand moisturizer is Dry Skin Hand Cream with glycerin, dimethicone (a skin protecting ingredient added to prevent water loss and protect an impaired barrier) and the palm oil emollient isopropyl palmitate.  It's a cleaver, non-greasy formulation that protects and hydrates hand skin.  I keep it in my lab coat pocket and I apply it numerous times a day to prevent dry skin from washing.

The bottom line is that to treat and prevent dry skin you need to protect it from water robbing circumstances.  You also need to moisturize it after bathing or washing to help recreate the water and oil content of healthy skin.

References: Lodén M."Role of topical emollients and moisturizers in the treatment of dry skin barrier disordersm" Am J Clin Dermatol. 2003;4(11):771-88. Imokawa G. Stratum corneum lipids serve as a bound-water modulator. J Invest Dermatol. 1991 Jun;96(6):845-51. Cho HJ. "Quantitative study of stratum corneum ceramides contents in patients with sensitive skin." J Dermatol. 2011 Oct 31. [Epub ahead of print] Photo: Thanks and gratitude to Hanaan Rosenthal