We hear the word immunity and usually, we think about vaccines, white blood cells, platelets, and infectious diseases. When it comes to our body, our immune system makes sure that it is healthy by eliminating foreign objects and invaders.

Being the body's largest organ, the skin is the first line of defense against the environment and has immune functions to protect the body from any foreign substance and various stimuli. Hence, it is important to make sure the skin's homeostasis—referring to the ability to maintain a relatively stable internal state that persists despite any changes outside—in order to make sure one maintains beautiful skin.

According to Dr. Junichi Hosoi, senior scientist at Shiseido, "Langerhans cells, which exist in the upper layer of the epidermis, detect foreign invaders and warn other cells to fire up the immune functions." These Langerhans cells, found in the upper layer of the skin epidermis, have two major functions that maintain the skin's homeostasis: Command function, where they control the immune system and go on defense mode when they detect foreign object intrusion, and Self-Defense function, which alleviates hypersensitivity of the skin to environmental factors, such as UV rays, dryness, and other skin problems.

While these Langerhans cells are vital to skin immunity, there are several factors that can diminish the power of these protective cells. As we age, factors such as stress, diet, radiation, and pollution can greatly affect our skin. So in the same way your body can be susceptible to germs and you may get sick, these irritant factors can penetrate the skin when the Langerhands cells are fatigued. As a result, the skin's condition and complexion suffers.

In practical terms, one may be able to take some measures with diet and lifestyle changes to strengthen and protect skin against damaging environmental factors like pollution. Practices like managing stress, not skipping meals, eating high-quality carbohydrates and antioxidant-rich foods, getting six to eight hours of sleep, and even bathing in a hot spring all help boost the skin's immunity for stronger, more beautiful skin.

When it comes to vitamins and supplements that promote skin health, no doubt the most important is building up your Vitamin A—it is responsible for cell differentiation, maturation, and growth. It is also important to add a brigade of antioxidants like Omega 3 and 6 to protect the skin from free radical damage.

When it comes to products, they don't actually affect your immune system—rather, they work to help increase your skin's defenses against external factors. Case in point: Shiseido Ultimune Power Infusing Concentrate.

Dubbed as "self-defense for your complexion," this product works by helping to protecting your skin from the outside against. The fluid also works to hydrate and smooth the skin for a fresh-faced effect.

Shiseido Ultimune Power Infusing Concentrate is targeted to try and help weakened skin using a combination of skin-soothing ingredients. CM-Glucan is a yeast derivative that’s been shown to help the skin with its natural self-protection. This is combined with complexion-soothing, ultra-gentle Bulgarian rose water.

Ultimune strengthens skin’s inner defenses with ImuGeneration Technology™ and Reishi Mushroom Extract. It can prevent damage from the stresses and strains of city life, and fight future signs of aging.