The reason eyeshadow slides into the crease of your eyes is because of oils, either naturally made by your skin, or from the makeup or organic and natural skin care products you put on your skin.
Keep moisturizers and skin oils away from your lids if you plan to wear shadow.
Don't Prime Eyes with Concealer or Foundation
A big mistake women make is to "prime" their lids with creamy concealer or their foundation. These tend to be too oily for the lids and only assist in the gradual slide of makeup into your crease.
The Amazing Wonderful Eyeshadow Primer
Primers are one of those beauty products that many of us swear by. Be sure to prime your face or your lids prior to eyeshadow application.