Lecithin is a substance found in egg yolks, milk, and some plant and animal tissues. It's been used as a medicine to treat various ailments for centuries, such as hypercholesterolemia (high cholesterol), liver disease, and asthma. Nowadays it's also incorporated into cosmetics like eye makeup and lipsticks. It's mostly made of three types of fatty acids: glycerophosphates (g-6-p), phosphatides (2-3-p), and triglycerides (t3). The glycerophosphates comprise about 40% of lecithin's weight.