If you've ever paid attention to the skin care ads on TV, you've likely heard at least one pitch for a product that promises to "hydrate your skin." But what does that mean? And why does your skin even need hydration?
Hydration refers to water. Your skin needs water to give it strength and elasticity -- in other words, to look and feel healthy.
Luckily, you've got a built-in barrier to hold in water. The outermost layer of your skin, called the stratum corneum, is made of dead skin cells called corneocytes, stacked like bricks. Fats called lipids act like mortar. This cellular "brick wall" helps to keep the moisture locked inside your cells.
The trouble is that the moisture-locking system doesn't always work as well as it should.
"Some people's lipid barrier is more prone to drying out," says Michael Cameron, MD, assistant professor of dermatology at the Mount Sinai Icahn School of Medicine. “When it does dry out, you can end up with scaly or flaky skin.”
Skin can get dehydrated if the cells underneath the barrier lose too much water. "When the water content inside the cells decreases, the cells become shriveled," he says. As a result, "The skin may look dull, lose its luster, and fine wrinkles can be more noticeable."
Dryness doesn't only affect your skin's appearance. It also can leave it itchy and cracked, which makes it uncomfortable to live with.
Why Does Skin Lose Hydration?
A loss of the lipids that normally seal in moisture can lead to dry skin. Atopic dermatitis, also called eczema, is a common condition where the skin barrier is more prone to losing its integrity.
Sometimes the things you do -- or don't do -- deplete your skin's water content, including:
- Spending time in the cold or heat
- Using harsh soaps, detergents, and chemicals
- Using rough sponges, washcloths, or exfoliating products
- Taking long, hot showers or baths
- Not drinking enough water
These problems are easy enough to fix. For example, you might drink a few extra glasses of water each day, keep your showers short and lukewarm, or minimize the use of soap, which strips the natural oils away from your skin.
Some medical conditions also lead to dry skin, including:
- Thyroid disease
- Sjögren's syndrome
- Poor nutrition
If you have one of these conditions, your doctor can help you find the right treatment.
Moisturizing vs. Hydrating: What's the Difference?
The terms moisturizing and hydrating are often used interchangeably. But are they the same?
"Moisturizing is really focused on the skin barrier itself," Cameron says. "These products work to seal in the water inside the cell."
These products contain three basic types of ingredients:
Humectants like glycerin, hyaluronic acid, and urea pull water from both the air and the deeper layers of skin into the stratum corneum to add moisture.
Occlusives like beeswax, soybean oil, and lanolin form a barrier that prevents water from evaporating.
Emollients like coconut oil, shea butter, and colloidal oatmeal add softness to the skin.
The newest generation of moisturizers also add ceramides or other ingredients to repair the lipid barrier and prevent water loss.
Hydration goes beneath the skin's barrier. It infuses water into the cells to "plump them up," Cameron says. Sometimes it can be hard to tell the difference because a lot of products incorporate ingredients that both moisturize and hydrate.
How to Keep Your Skin Hydrated
To improve the look and feel of your skin, you want to attract moisture inside and keep it there. Here are a few ways to do it:
- Limit your showers to 5 or 10 minutes in lukewarm water.
- Use gentle soaps, laundry detergents, and cosmetics.
- Turn on a humidifier during the winter.
- Drink extra water throughout the day.
If your skin still looks dry and flaky, apply a moisturizer or hydrating mask. Before you buy any skin care products, though, know your skin type: oily or dry. "You want to avoid products that can clog your pores," Cameron says. "That can lead to acne, and the products we then have to use to treat it can sometimes dry you out even more."