Oily skin is an over functioning of the sebaceous glands (oil producing glands) distinguished by a shiny appearance and break out. Sebaceous glands produce more oil than required for lubrication. Oily skin has enlarged pores, and is prone to black heads. Skin has a coarse, thick look.

Oily Skin Types:

Skin is the largest organ of the body. There are five different types of skins learning to know one’s skin type helps in looking after it.
Type 1: Oily Skin
Oily skin is characterized by a shine on face, skin is often thick, and has large pores. Oily skin is prone to blackheads and blemishes. It occurs more in men than in women, and it predominantly affects adolescents.  Excessive lipids or oil is due to over productive sebaceous glands.
Type 2: Combination Skin
Sebaceous glands are unevenly distributed, being more in numbers around the scalp, on the forehead, along the nose and on the chin, and lesser on cheeks and neck, and around the eyes. Resulting in patchy skin. This is called combination skin. Combination skin is rather dry in some parts of the body and oily in other localizations. Mixed facial skin tends toward dryness on the cheeks and around the eyes while being oily in the t-zone (nose, forehead, and chin). This skin type is common. The patchy or combination skin has two different types of distribution:
1) Normal to Oily: People with normal to oily skin generally have normal skin on their cheeks and oily skin with enlarged pores on their T zone (the area that spreads across the forehead and down the nose and chin). Skin type it has medium pores, a smooth & even texture, good circulation, healthy color, may tend toward normal on the cheeks while being oily in the t-zone.
2) Dry to Oily: This skin type is marked by oily skin in the T zone and dry, taut skin on the cheeks. it has medium pores, a smooth & even texture, good circulation, healthy color, may tend toward dryness on the cheeks while being oily in the t-zone.
Type 3: Sensitive:
Sensitive skin” is not a skin type, but it is a symptom of allergic reaction. Sensitive skin tends to be thin, delicate with fine pores. It irritates easily and is often red and blotchy.  It is prone to broken capillaries, is frequently allergic.
Type 4: Dry
Dry skin feels tight, especially after cleansing, & has fine wrinkles, red patches
Type 5: Aging or Sun-damaged
This skin also feels tight with visible wrinkles, slack skin tone, has leathery texture & broken capillaries.

Causes for oily skin:
Hereditary: The amount of oil that an individual makes is determined by genetics.
Diet: A diet rich in oil and fat can cause oily skin.
Hormones: Hormones affect oil production. The oil gland is considered the end organ because it is this gland that is acted upon by hormones. Hence it is called an "end organ response".  Though people may have the same level of hormones, but produce different quantity of oil because their oil glands respond differently. This are the following conditions when hormonal levels change:
Puberty: During adolescence, an increase in the level of sex hormones, known as androgens, causes increased production of oil. The reason for this is that androgens enlarge and stimulate the sebaceous glands, causing them to produce more sebum. Because of this hormonal change in adolescence, oily skin is common in teenagers.
Menopause: During menopause there is a decrease in the amounts of estrogen produced and an increase androgen. Androgens stimulate sebaceous glands thus causing oily skin.
Menstruation: Before periods also estrogen levels are low and thus they can also upset the oil balance and increase the activity of sebaceous glands. 
Birth control pills: These pills are made of hormones and thus change the hormonal balance.
Cosmetics: Cosmetic containing called isopropylmyristate can cause oily skin.
Incorrect, insufficient cleansing: Sleeping with make up on or using harsh products to clean can stimulate over production of oil.
Atmospheric conditions: Humid and warm climate stimulate production of oil.
Medical Causes: Hepatic (Liver) and endocrine malfunction can change the hormonal balance. Infections can also lead to oily skin. Even physical stresses, such as colds, allergies, surgery can cause more oil production.
Nervous stress: Studies have shown that the body produces more androgens when a person is under stress. The triggers sebaceous glands to pump out more sebum.

Remedies For Oily Skin:
1) Cleaning: It is very important to keep your skin clean. Wash it at least twice a day. Use a mild cleanser or an oil free soap. This will prevent clogged pores and reduce pimples.
2) Astringent: Use an astringent without fail. This removes the extra oil from the skin, making your skin look good.
3) Professional help can be taken. Consult a dermatologist and also you can visit an expert once a month for a good face clean.
4) Water Intake: Drinking water helps your skin to glow. You should drink atleats 8-10 glasses of water. This keeps your skin moisurised, and flushes all the toxins from the body.
5) Eating the right food is one of the important remedies for oily skin. Fried and oily food will tend to make your skin oily. Thus avoid that and eat more of green vegetables and fruits.
6) Home remedies. There are various home remedies for oily skin. They include home made packs like Egg White applied on the face and kept for 15 min will help you to get rid of the oily face. Lemon juice and honey, a very good remedy for oily skin. The juice of Neem Leaves is also another remedy for oily skin with pimples.
7) Cucumber Juice is a great pack not only to avoid oily skin but it makes your skin look fresh and glowing. It should be kept in the fridge and then apply.

Oily skin tends to age more gradually than dry skin. The oil on the skin helps the skin and protects it from the fine lines and wrinkles. A well balanced diet and a simple skin care routine will help you avoid oily skin.