Since the days of Dep, hair gel has been a popular, versatile styling product often used for firm hold and a slick finish. There are several caveats to using gel as a styling product, including some long-term effects of overuse.

Styles on Which to Use Gel

Short styles and spiky looks are most suited to the usage of gel for the simple holding effect. Gel should be used very sparingly on long locks, as it will create an odd stiffness and lack of movement if applied throughout the body of hair. Some intricate styles, such as Mohawks or finger waves, require a larger application of gel, as hold is essential no matter the length.

Chemical Composition

The main component of hair gel is water, which is what gives fresh gel its viscosity. Other ingredients are polymers, plasticizers and wax. Some products contain denatured alcohol in the form of parabens. (Ref. 2.)

Damaging Effects

At its mildest, the fragrance and filler used in hair gel can be an irritant to those with allergies. The alcohol and plasticizers in gel are drying to the hair and scalp, and other minor chemical components have been shown to affect everything from fertility to kidney function. (Ref. 2.) Consider that these chemicals are also flowing down the drain each time gel is washed from your hair.

Other Common Styling Products

Hairspray, mousse, pomade, wax, cream and clay all have their specific uses as styling products. Each has a different degree of hold between each product, and also certain firmness levels within each type of product.

Alternative Products

Heavy conditioners or leave-in conditioners can be combed through already dry hair to set certain styles, such as a pompadour. Homemade hair gel can be created with unflavored gelatin packets added to boiling water, cooled and applied to a style, as used by professional swimmers. Elmer's classic white school glue is also useful for gravity-defying styles, though any damaging effects are relatively unknown.

Source:

Hair Gel (Wikipedia)

Harmful Product Chemicals

Hair Products and the Environment