The body’s overlooked defense system

Make the most of your skin barrier to ward off certain types of disease. Hint: It pays to moisturize.

Picture it: You're the body's military commander, and you're reviewing your protective forces. Immune system? Check. Stomach acid? Check. Beneficial gut bacteria? Check.

Don't forget to include your skin: it's one of the most important bastions in the fight against disease, keeping harmful organisms and substances from getting inside the body.

Unfortunately, our skin weakens as we get older, and it requires more effort to keep it healthy. That job can take a back seat if you're busy tending to other health issues or you're unsure of how to care for your skin.

With infection on everyone's mind, it's time to refocus attention on the skin and strengthen your defenses.

Important soldiers

The skin consists of three layers:

• The deepest layer (subcutaneous tissue) is made of connective tissue and fat, and provides insulation, energy storage, and shock absorption.
• The next layer (the dermis) contains collagen and elastin, blood vessels, nerves, sweat and oil glands, and hair follicles.
• The topmost layer (the epidermis) is built to be a barrier. It consists of five different layers of its own, each with cells constantly rising to the top part of the epidermis, called the stratum corneum — the skin we can see and a major part of the body's defenses.

Within the stratum corneum are up to 30 layers of flat, dead, protein-filled cells that mix with fat and water to create a sort of brick-and-mortar matrix. It keeps moisture in the body and protects us from toxins, ultraviolet rays, and bacteria.

Weakened defenses

A number of factors can weaken the stratum corneum. One is aging. "The skin gets thinner, and the cells get flatter. Older skin has a lower water content. Fat diminishes and shifts, so everything is less vigorous and strong, particularly in areas of sun exposure," explains Dr. Kenneth Arndt, a dermatologist and a prior medical editor of the Harvard Special Health Report Skin Care and Repair.

Dr. Arndt says heavy use of certain medications — such as topical, oral, or inhaled steroids — can also thin the skin. Inflammatory skin disorders, such as eczema (atopic dermatitis), can reduce the amount of fat in the stratum corneum, weakening the skin barrier.

And frequent hand washing or exposure to cleaning solvents or alcohol found in hand sanitizers can dry out and damage the skin surface. "The skin gets dry because soap can wash away fats in the skin," Dr. Arndt says.

In other words, what we need to do to protect our health in the COVID-19 pandemic simultaneously threatens the health of the skin of our hands.

Invasion risks

Dry, thin skin is more permeable than plump, healthy skin, and it can crack or tear easily, like tissue paper. "Any time the skin splits or is excessively dry, that's an avenue for an organism to get in and cause problems," Dr. Arndt notes. He says the coronavirus that causes COVID-19 is not contracted through the skin. But other types of bacteria can make us sick if they breach the skin barrier, such as Staphylococcus aureus or Streptococcus pyogenes.

These bugs may cause a type of infection called cellulitis in the skin tissue. Left untreated, the infection can spread to other parts of the body, causing fever or swelling, and increasing the risk for sepsis and hospitalization. Fighting back requires powerful antibiotics.

Rally the troops

Before you find yourself in the midst of battle, try fortifying your defenses. Dr. Arndt says the best way is to lock in moisture. "When you add moisture, the skin gets fatter and more flexible," he says. "The trick is keeping it that way."

He recommends moisturizing your skin right after you've bathed or washed your hands (which adds water to your skin). "Petroleum jelly is excellent at sealing in water, but it's aesthetically not pleasing," Dr. Arndt points out. "Creams contain water, oil, and emulsifiers to keep the ingredients mixed together, for ease of use. But things that aren't greasy don't work as well or for as long."

Here are some other options:

Skin creams with ceramides. Ceramides, a type of fat, are a main component of the stratum corneum.

Moisturizing oils, such as mineral oil. These have the same effect as petroleum jelly without being as greasy.

Products with humectants. These substances help bind water to the skin for absorption. The ingredients to look for: glycerin, urea, pyroglutamic acid, sorbitol, lactic acid, -lactate salts, or alpha hydroxy acids.

Other plans of attack

In addition to moisturizing your skin throughout the day, Dr. Arndt suggests avoiding sun exposure and using sunscreen while outdoors.

He also recommends getting a humidifier to add moisture to the air, especially in the fall and winter as the humidity drops and the dry air sucks moisture out of your skin.

And while staying hydrated is crucial to the health of all cells in the body, Dr. Arndt says that keeping water from leaving the skin with creams, oils, and humectants is what's needed; drinking excessive amounts of water won't hydrate the skin.

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