What Causes Greasy Hair? 9 Causes & How to Fix It

1. Brushing: Brushing your hair too much can stimulate sebaceous glands and increase oil production.
2. Touching: Touching your hair too much can cause oil to spread from your fingers to your hair and make it look greasy.
3. Products: Using too many hair products can lead to product buildup. Avoid overdoing it with dry shampoo because the powder may initially absorb the oil but later make it look even more greasy.
4. Over-washing: Washing hair too frequently removes necessary oils and can dry out both your hair and scalp. When your scalp is dry, it signals the sebaceous glands to produce more oil.
5. Over-conditioning: Over-conditioning can weigh hair down, and increase oil production. Since your hair naturally has oil at the roots, avoid applying conditioner on your roots and concentrate it on your ends instead. Make sure to rinse thoroughly. 
6. Skin conditions: Some people may have overactive sebaceous glands on the scalp. The oil can then attract debris, increase dandruff, and make the hair clump together. In some cases, the sebaceous glands can block the hair roots, resulting in significant hair loss and dandruff.
7. Pillowcase: Your face secretes oils onto your pillowcase, and as you sleep, your hair can absorb some of that oil and look greasier than usual in the morning. Make sure to regularly wash and change your sheets.
8. Hot water showers: Avoid hot water showers, since hot water can irritate the scalp and may cause redness, itchiness, and excessive oil production
9. Diet: Your hair health may reflect your diet. For example, eating too many omega-6 fatty acids can cause your hair to be greasier than if you are also eating omega-3 fatty acids. Try to eat a balanced, healthy diet to promote not just hair health but overall health.

Making slight changes in your hair habits can help you retain natural oils without the grease. Tips for healthy, shiny hair include the following:

• Shampoo 1-2 times a week with a cleanser made for oily hair. If you work out every day, you may have to wash your hair more frequently because sweat and grime will make your hair look greasy. In that case, make sure you find a mild shampoo that is gentle to your scalp.
• Some shampoos contain ammonium and sodium lauryl sulphate. Such shampoos are to be used only on oily scalp because they can cause dryness.
• When washing, gently massage your scalp and let the lather sit for a few minutes before rinsing. If your hair still feels greasy, repeat with another session of washing.
• Use conditioner in small quantities and work it into the middle of the hair shaft and tips, not the roots and scalp.
• Brush your hair gently. Avoid touching your scalp with the brush or comb when moving it through the hair. This reduces or prevents oil from moving from the scalp to the hair.
• Managing stress can help reduce oil secretions as well.

If you experience persistent irritation and inflammation of the scalp, seek the advice of a doctor.