Shampoo is a type of cleaning agent that is used on hair. In most cases, the cleaning agent comes dissolved in a liquid. The liquid solution is massaged into wet hair, and creates a lather that breaks up deposits of oil and dirt. The lather is then rinsed from the hair after a few minutes, leaving the hair clean.
Shampoos have a number of qualities that should be considered before use. How well a shampoo cleans is very important, and individual brands usually come in slightly different formulations for either “normal” or “oily” hair. The fragrance that a shampoo leaves in the hair is also a major consideration, and is why scented shampoos are so popular. Other factors often taken into account include how shiny the shampoo makes the hair, possible irritation of the scalp, toxicity, price, if organic ingredients have been used, and whether or not the shampoo has been tested on animals.
There are many different categories of specialty shampoos, with each type claiming to have properties beyond cleaning hair. A few of these categories are: lice killing shampoos that help get rid of lice infestations; anti-dandruff shampoos that often contain fungicides, chemicals that can assist in removing white flakes in hair; clarifying shampoos that remove hair-care product buildup; baby shampoos that are specially formulated to be gentle; thickening shampoos that purport to make hair fuller; straightening shampoos that make hair less curly; 2-in-1 shampoos that contain conditioners; and dry shampoos that can be used without water.
Modern shampoo is not made out of traditional soap. Although earlier versions did use soap shavings, traditional soap-based shampoo made hair dull and irritated the scalp. Modern shampoo is formulated using chemicals and fragrances that balance the ability to clean hair with other factors including scalp irritation and superficial look. By leaving some oil in the hair, being slightly acidic, rinsing cleanly, and not irritating the skin, the chemical composition of modern shampoo has shown itself to be far superior to that of the soap-based original.