If your hair becomes oily and sticky within 1-2 days of washing it, then you probably have greasy hair. It is a problem not only for the appearance, but also for the health of your mane. Scalp naturally secretes oil as a way to keep your hair shiny and oily. But if there is too much oil, the hair becomes greasy, limp and stringy.
Heredity, excessive stress, hormonal changes, poor hair care routine and eating oil-rich foods are some of the factors that can lead to greasy hair. Such hair is more prone to itchiness and dandruff, and looks heavy, unmanageable and unclean.
Here are some scientifically proven fixes for greasy hair.
If you have greasy hair, you need to wash out its excess oil almost everyday. You need to keep your hair and scalp clean, so that oil does not accumulate in your tresses. As shampoos have a drying effect on your mane, leave them on for about 5 minutes before rinsing. 
Brushing or combing your hair too much can over-stimulate your scalp’s oil glands, and cause them to secrete more oil than needed. The more you brush your hair, the greasier it will become. Greasy hair does not tangle quickly, so you don’t need to detangle it every hour. Even if you need to comb your hair, give it a gentle comb instead of brushing it continuously. A wide toothed comb is better than a bristled brush, as the former will distribute less sebum on the scalp 
The main aim of conditioners is to keep your hair moisturized. As you have oily hair, the extra oil your scalp is producing is enough for moisturizing your hair. If you use a conditioner on your hair, it will only add to the oiliness of your scalp, thus making your hair greasy faster, and the condition more terrible .
Hormonal imbalance is one of the causes of hair greasiness . There may be several factors affecting your hormones, such as birth control pills, stress, certain medications or treatment procedures, etc. Identify your cause, and rectify it if possible. For instance, if you are taking birth control pills, try to change to a different brand, or use another form of contraception.
Your hands have oil in them, which you may transfer to your hair if you touch it too often. Touching it again and again will also stimulate the oil glands, thus causing them to secrete more oil. So, try to keep your hands off your hair as far as possible.
These are some fixes that scientists have proved to work for greasy hair. Follow these tips wisely, which will help you manage your oily hair easily, and have a smooth looking mane.
. Oily hair: MedlinePlus Medical Encyclopedia. 2016Oily hair: MedlinePlus Medical Encyclopedia. [ONLINE] Available at: https://www.nlm.nih.gov/medlineplus/ency/article/002042.htm. [Accessed 10 February 2016].
. Essentials of Hair Care often neglected: Hair Cleansing. 2016.Essentials of Hair Care often neglected: Hair Cleansing. [ONLINE] Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3002407. [Accessed 10 February 2016].
. Oily hair: MedlinePlus Medical Encyclopedia. 2016.Oily hair: MedlinePlus Medical Encyclopedia. [ONLINE] Available at: https://www.nlm.nih.gov/medlineplus/ency/article/002042.htm. [Accessed 10 February 2016].