As the body’s largest organ, the skin performs a series of key functions resulting from multiple chemical and physical reactions that take place within it. The skin is a barrier, protecting the body from the elements, injury, and oxidation. It helps maintain a constant body temperature by helping the body adapt to different ambient temperatures and atmospheric conditions through the regulation of moisture loss. It gathers sensory information and plays an active role in the immune system, protecting from disease.
In order to play all of these functions—protective, metabolic, sensory, and immunological—the skin must maintain its own auto-repairing capacities and functional integrity. Cosmetic products are very important to the skin’s protective function. Sunscreens protect against UV radiation and, therefore, against premature skin aging and skin cancer. Creams and lotions with a bactericidal effect reduce and/or control excessive proliferation of bacteria on the skin, a problem particularly associated with oily skin, and one of the main causes of acne development. And, by forming an invisible barrier on the skin’s surface, specific moisturizing ingredients can help reduce the skin’s moisture loss that results in dehydration. The skin also protects internal organs from exposure to oxygen. Without the skin, the body’s organs would rapidly oxidize, much like a peeled banana or apple does when its interior is left exposed to air.
Through the secretion of sweat and sebum, the skin performs an excretory function, eliminating a number of harmful substances resulting from the metabolic activities of the intestine and the liver. The skin also secretes hormones and enzymes.
When the skin’s chemistry and chemical composition are not compatible with a particular product’s ingredient(s), the result is overall product sensitivity and even allergic reactions.
The large number of nerve endings in the skin makes it sensitive to touch. As a result, the skin is a sensory organ and the point of receptivity for cold, heat, and pain.
The skin plays an immunological role, primarily through the Langerhans cells, which carry antigens from the skin to the lymphatic system. Excessive UV radiation either destroys or inhibits the performance of Langerhans cells, increasing the risk of skin cancer.
The skin tends to be discussed and treated as an entity unto itself, so this close relationship between the skin and the body is often overlooked or forgotten. Although it protects the body in a variety of ways, the skin and its condition are governed by a number of internal body functions. For example, skin oiliness arises from oil gland hyperactivity. Pigmentation problems are due to the tyrosinase enzyme, and are regulated by hormonal functions. Given this relationship between the skin and the body, for the skin to look its best, there is a need for overall health through proper nutrition, exercise, and rest. This connection also highlights the potential problems that ingredients penetrating deep into the dermis may cause if they are systemically absorbed by the capillary system.
When the skin performs in perfect harmony, the result is a
beautiful, glowing, healthy complexion. If the skin is not in harmony because of deterioration due to age, sun damage, bacterial infection, hyperkeratinization, or simply loss of natural moisture, cosmetic products are meant to assist in restoring its balance and beauty. They must do so, however, by working in conjunction with the skin’s very complex structure.