The best offence is a good defence

As the body’s largest organ, skin’s primary role is to maintain a healthy barrier between you and potential harm from the elements, including sun and rain, bacteria and germs, and stress. But are you protecting this important ally of your immune system?

Skin: A complex system of protection

The skin comprises three major divisions or layers, including the epidermis, the dermis, and the hypodermis.


This layer of your skin is the part you can see and touch. Despite the fact that it can be about as thin as tissue paper, the epidermis itself contains five sublayers. The uppermost sublayer is the stratum corneum, and it’s the first line of immune defence.


Skin’s middle layer, or dermis, houses collagen that gives your skin strength as well as elastin that provides flexibility. Nerves located here keep you safe by triggering pain or letting you know, for example, when your hand is too close to the stove.

Hair follicles are rooted in the dermis, as well as oil and sweat glands. They play critical roles in your immune defence. Oil, for example, may help to seal hair follicles so that unfriendly microbes can’t enter deeper layers of the skin. It also helps repel water. Sweat helps you maintain a healthy body temperature.


The hypodermis (also known as the subcutis or subcutaneous layer) is the deepest skin layer and consists primarily of connective tissue and fatty tissue. This layer allows skin to move smoothly over tissue and muscle and to act as a shock absorber. The hypodermis also insulates your body to protect you from the cold.

Skin’s microbiome

Given its extensive surface area, skin provides room and board to millions of bacteria. This adds an extra layer of protection, as these bacteria help prevent colonization and invasion by pathogenic microbes.

Barrier breakdown

Despite various skin fortifications, barrier function can be compromised—and it might start with simple water loss. H2O deficiency is associated with skin dysfunction, including atopic dermatitis and skin wrinkling. To keep skin healthy, you want to drink plenty of water and minimize transepidermal water loss or the moisture lost from skin cells through evaporation.

There are a lot of things working against that goal, such as stress and pollution. Certain topicals can also cause a breakdown in barrier function. Common foaming agents such as sodium lauryl sulphate and sodium laureth sulphate can strip away valuable moisture and cause skin irritation. Alcohols such as isopropyl alcohol, propanol, and benzyl alcohol may also rob your skin of moisture.

To lock in moisture, look for skincare helpers that mimic the natural lipids found in your skin. Borage, carrot, and evening primrose oil are rich in fatty acids. Try camelina oil, which is high in vitamin E and a rare plant source of omega-3 fats.

By Lisa Petty, PhD