The skin is the largest organ of the body. We tend to fuss over it many times a day, yet most people don't have a good understanding about proper skin care. Here are some key facts.

The skin is composed of two main layers. The top layer is called the epidermis. This layer is quite thin (about one millimeter) but provides several essential functions. The epidermis forms a strong barrier and helps protect our bodies from the outside world. Pigment cells in the epidermis help protect us from harmful ultraviolet rays of the sun.

The immune system is also part of the epidermis. If we get a cut or a scrape, harmful bacteria are kept in check which reduces our chances of getting an infection. The lower portion of the skin is called the dermis. This portion is quite thick in some areas, such as the back, but can be quite thin in other locations such as the eyelids. The dermis is mainly made up of a resilient tissue called collagen. Elastic tissue provides flexibility. Try pinching your skin. Notice how it snaps back to its normal shape. The dermis also contains nerves, blood vessels and glands. Underneath the dermis is the subcutaneous fat.

When we are young the skin is smooth and firm, primarily because the skin does a good job of trapping water. Over time, the skin starts to thin and dry out. Facial muscles responsible for smiling, frowning and squinting eventually cause creases to appear between the eyebrows and around the eyes and mouth.

skin types

Each person has its own skin type, which is a natural combination of three factors:

1. Water content (is responsible for skin's suppleness and comfort)
2. Lipid content (is responsible for nutrition and softness)
3. Level of sensitivity (is responsible for skin's resistance and tolerance)

Normal Skin
Normal skin has barely visible pores and radiant pinkish complexions, with no imperfections. Normal skin has an adequate amount of water and lipids, an adequate balance between them, and a moderate sensitivity level.

Normal skin is achieved by the ideal balance between the rate of sebum production and cellular exchange.

Dry Skin
Dry skin has almost invisible pores, and a dull, rough complexion with red patches. Dry skin is sometimes normal and not oily, but sometimes can be fine and delicate. Alternately, this skin type is temporarily dry when exposed to physical elements such as sunburn, burns, cold temperatures, abrasions, and certain medications. When the skin repairs itself after being exposed to these elements, dryness and flaking usually occurs, and sometimes itchiness. Certain people suffer from a dry-skin condition that runs in families. Their skin doesn't itch, but the disease causes their skin to flake and sometimes to crack.

Dry skin is caused by genetic or hormonal aging, as well as external factors such as wind and UV radiation.

Very Dry Skin
has almost invisible pores, and a dull, rough complexion with red patches. More severe dry skin may be rough and scaly. The outer skin layer may develop tiny cracks, mainly on the back of the hands, outer sides of the arms, forearms, and legs.

Very dry skin is caused by genetic or hormonal aging, and external factors such as wind and UV radiation.

Normal, Combination Skin
The pores of normal, combination skin are overly dilated, tend to have blackheads and be shiny in the T-zone. The skin is either overly dry or excessively oily, with occasional roughness on the cheeks. The oiliness and dryness can change, too, depending on the time of year (skin is usually drier when the weather is cold). Even oily skin can become rough and irritated in winter.

Combination skin is caused by an imbalance in the production and distribution of lipids (due to hormonal and genetic factors).

Oily Skin
Oily skin has dilated pores, dull complexion, shiny complexion, blackheads, and pimples. The oiliness of the skin can change from day to day, depending on the sun, the wind, time of the year, and the weather. The oil glands produce excessive lipids. This type of skin appears shiny, thick, or slightly waxy. Touching oily skin may sometimes leave a residue of oil on the fingertips. Often a chronically oily skin has enlarged coarse pores and pimples and other blemishes. It is prone to blackheads.

Oily skin is caused by hyperactivity of the sebaceous glands that produce more oil than is needed due to puberty or other hormonal imbalances, stress, antibiotics, and exposure to heat or excessive humidity.