Naturally occurring oils in the hair are nature's conditioner but these oils can easily transfer to other surfaces, such as a leather couch. Since leather is a natural material, it's absorbent and the hair grease can soak into the surface. Complete removal of hair oils or other hair products from your couch can only be achieved when the grease is removed both from the surface and out of the leather fabric itself.
Cover the grease stain on your leather with cornstarch. Leave the cornstarch there for 20 minutes. Brush the cornstarch off and into a trash bag, then place more cornstarch over the grease spot and leave it overnight.
Brush off the cornstarch and throw it away. Dampen a clean, dry cloth with undiluted white vinegar. Wipe the site of the hair grease stain on your leather couch to remove the cornstarch dust, as well as any remaining grease.
Fill a bucket with warm water and add enough mild saddle soap to make suds.
Wash the stained area with the saddle soap solution.
Dampen a clean cloth with water. Wipe down your couch to rinse the soap solution off thoroughly. Dry off the couch with a clean towel.
Talcum powder and baking soda can also be used to absorb a grease stain. Rubbing alcohol swiped over a stain will also cut through grease. Substitute a drop or two of mild, grease-cutting dishwashing detergent for the saddle soap if you cannot find saddle soap.
A grease stain that's left on your leather sofa will become dark and discoloured and will attract more dirt.