In oily skin, the oil producing sebaceous glands are overactive and produce more oil than is needed. The oil oozes and gives the skin a greasy shine. It can be caused by heredity, diet, hormone levels, pregnancy, birth control pills and hot and humid weather. Oily skin needs special cleansing with plenty of hot water and soap to prevent the pores from being clogged. Avoid harsh products that strip your skin of oil and encourage flakiness. They can cause a reaction known as reactive seborrhoea, where the oil glands work overtime to compensate for the loss of natural oils.
Avoid skincare products that leave your skin feeling taut and dehydrated. You can use cetaphil and make sure that the rest of the times you wash your face with fresh water. Avoid heavy greasy moisturizers and take a diet rich in proteins but restricted in sugar, fluids and salt. Drink plenty of quality water to keep the skin hydrated and flush out toxins.
I hope it helps. Take care and regards.