I googled and found a few things you could try.
Mayonaise - it says to allow the mayo to sit on the area for a few minutes (the longer the better) and then rinse.
Pure soaps in bar form (Ivory or Dove) - work into a warm lather and rinse....repeat until sap is gone.
Baking soda - apply baking soda to a warm, damp rang and rub vigorously to affected area.
Crisco - apply to area, let sit then rinse with warm/hot water. You would probably then have to wash with something to remove excessive oil.
Pine oil - moisten a washcloth with pine oil and rub on affected area.
Tea tree oil - a few drops applied to affected areas should dissolve the sap. Rub it in then comb through with a fine tooth comb.