Clean it with dish washing detergent or any other domestic cleaning product . That answer may surprise you, but many household detergents are made from grease or fat.
When products like this are used on carpet fiber and not extracted or removed correctly, they act like a magnet by attracting more dirt and grime. I’ve had many clients tell me that after having their carpets cleaned the original stains have reappeared and are now larger. Once the carpets are dry the soapy residue wicks to the tips of the fiber and settles on top
If you’ve had this happen, pour a small amount of water onto the spot, gently agitate with your fingers (sometimes the soap will re activate) and then blot with an old towel or micro fiber cloth. You should be able to see the dirt and grime lift out onto the towel. The area should look cleaner and feel less sticky.
Please note: the image used in this blog is for demonstration purposes only. Dish washing detergents are made to wash dishes not carpets.