Sebum (so-called oil) is a mixture of oil secretions released from the sebaceous gland cells and lipids from the epidermis, but mostly it consists of sebum derived from the sebaceous glands. It is said that 2.0 to 0.1 γ / cm / min of lipids are excreted from the sebaceous glands and 0.4 to 0.05 mg / cm of them are accumulated on the surface of the skin, which become a sebum film and protect the skin from stimulation.

Dry and greasy skin are caused by the difference in the amount of sebum secretions. The amount of sebum secretions varies depending on climate, age and environment. At the turn of the season, temperature and humidity changes are so intense that it becomes impossible for the skin to respond to it properly, which makes it easy to cause roughness on your face.

In summer with high temperatures, sebum and sweat secretions are active, which causes greasy skin on your face. In the winter it is dry, and the secretion of sebum decreases considerably, so the skin tends to get coarse. The amount of sebum secretions is not fixed, and it tends to decrease with age, yet sometimes the amount temporarily increases depending on your physical or mental condition.

It is not excess. The skin film creates a thin layer rich in lipids, covers the surface of your skin and hair and smooths out to prevent from drying. It also helps to prevent moisture intrusion.

It has also disinfection effects. When you touch your face, you could feel that there are an oily part and a part that tends to get dry (especially around the eyes). Skin trouble can be prevented by removing oil from the greasy part of your face.

The T-zone area which is from the forehead to the nose produces sebum the most. It can bother you. The shininess is caused by overproduction of sebum which prevents foundation from sitting well on your skin and makes the skin look unpleasantly shiny like a mirror.

It is necessary to take care of each part of your skin differently.

Even people with dry skin can get shininess just on the T-zone. It is important to use a different skin care product for the T zone that tends to get greasy and the part of your face that tends to get dry. For example, it is best to temporarily regulate sebum with astringent toner, avoid using a skin care product that contains oil such as milky toner and rich cream for the greasy part of your face and to remove sebum with oil blotting paper.

In general, most Japanese people have combination skin that the T zone is oily but the cheeks and around eyes are dry. The oil on your skin doesn’t have a negative effect, however it causes troubles like shininess and prevents foundation from sitting on the skin with excessive oil. But sebum, when mixed with sweat, sucks more dust and dirt than sweat, and it only makes your skin dirtier.

The fineness of the skin texture is determined by the gene. People with rough skin have the pores opened somewhat larger. If the pores remain dirty, the pores become more noticeable and turn into black acne which make your skin look dull. Black acne is caused by dirt stuck in the pores with accumulated sebum which makes it look black.

You can prevent it by cleaning the pores so as to tighten them. After cleansing and washing the face thoroughly to remove the dirt from the surface of the pores, apply toner to cool and tighten the pores every day. Repeat this process at least twice a day. It is good to pad your skin with tonner with cotton. Tighten your skin thoroughly especially when washing and before makeup.

The fluctuation of male hormone secretions activates the function of the sebaceous glands and the sebum secretions become more active. At the same time the pores are blocked with keratin and the sebum and keratin are accumulated in the pores. As a consequence, acne begins to appear on the face. It gets red when it's inflamed by bacteria.

First, the sebaceous glands mature and enlarge at puberty. Keratinization of the pores increases and clogs the pores. The inside of the blocked pores expands and fills with keratin and sebum. Bacterial infection causes inflammatory acne, and skin pigmentation occurs after it's suppurated. It leaves a scar on the skin if it's severe. It can be caused by genetic makeup, increased sebum secretions, insufficient facial cleansing, pores blocked by dirt or toner, hair, external contact stimuli getting from resting the cheeks in the hands, sleep deprivation, overeating, nutritional imbalance and etc.

Some of the precautions you can take are: to wash your face with soap in the morning and the evening, to avoid irritating acne, not to stay up late, to sleep enough, to keep the daily routine, to avoid cosmetics containing excessive oil and simply use only a toner instead ( if you really need to apply more than toner, take them off as soon as possible), to avoid imbalanced diet and overeating and to refrain from eating spices and drinking alcohol, and it is also important to keep your hair from touching your face.