From slick to spiky, gels and other styling aids create looks that your hair left alone would never accomplish. Gels work their architectural feats using polymers -- that is, plastic -- dissolved in alcohol. Alcohol can weaken keratin and strip hair of moisture and oils. That damages keratin, leaving hair weak and brittle. Use gels sparingly, preferably those that are alcohol free.
Pomades and waxes, on the other hand, contain heavier ingredients like petroleum jelly and beeswax. Removing them may take repeated washings or a stronger shampoo than you would otherwise use, which can also damage hair. Newer, water-based formulas help avoid this problem. But remember: A little goes a long way.