A shampoo ingredient list as long as your arm can leave you in a lather when you try to determine what's best for your hair. The bulk of a shampoo bottle's contents is water, which provides a fluid base for the ingredients that clean and condition your hair. Shampoo components work in tandem to suds up, strip away dirt and oils, infuse moisture and leave a fresh scent.
Down and Dirty
The most basic purpose of shampoo is scrubbing hair clean of the day's dirt and excess oils. This is where the surfactants in the ingredient list come in. Ingredients such as ammonium lauryl sulfate or sodium lauryl sulfate result in a pleasing pile of suds, but these chemical detergents, which are found in some household cleaning products, can contribute to itching and redness. Some stylists contend that sulfates harm color-treated hair or other salon processes and contribute to frizz. Producers of sulfate-free shampoos strip out these detergents, replacing them with other ingredients that are milder and typically used to thicken the formula's consistency. Oils derived from nuts and seeds can clean naturally by breaking down the buildup of oils in the hair. Citric acid and sodium citrate are used to keep shampoo at the proper pH balance.
A big, sudsy lather doesn't necessarily indicate how well a shampoo is cleaning and conditioning your hair, although items in the ingredient list not only create bubbles but keep them long lived. The sulfates that clean hair contribute to foam as well as the secondary surfactants, including detergents that are less harsh but more controversial such as cocamide DEA. Natural surfactants such as lactylates make the foam bigger and richer. In addition to adding thickness to a shampoo formula, gums such as guar gum and xanthan gum sustain foam. Other ingredients that lend more to the rich, thick look and feel of a shampoo than to its performance are glycol distearate, polyglycol esters and sodium chloride.
Picking a formula geared toward your hair type is important. Shampoos for fine hair have more cleansing agents and less conditioner to not weigh the hair down, while cleansers for thick, coarse or curly hair saturate strands with conditioning agents. Glycerin locks in moisture, while cetyl or stearyl alcohol -- unlike the drying agent isopropyl alcohol -- lubricate the hair shaft for easy combing. Powered by vitamin B, panthenol contributes shine, moisture and thickness. Silicones such as dimethicone thicken and smooth strands while making detangling easier. The softening agents in compounds such as quaternium give hair a silky and shiny appearance.
Unless you select a natural shampoo free of all fragrance and colors, herbal oils or artificial scents and coloring agents are added to infuse a touch of scent or make the product prettier. To make sure that the shampoo has a shelf life, preservatives such as benzyl alcohols, parabens or urea derivatives can be added to guard against bacterial growth. Parabens are controversial ingredients linked to breast tumors in one study, but the Food and Drug Administration says they are safe for use.