Shampoos are used to remove dirt, dead skin and excess oil from the scalp and hair, and leave the hair attractively pliant and glossy. Most shampoos today contain a detergent as the cleansing agent. Other ingredients commonly include chemicals added for specialty purposes a consumer may find attractive:
- Conditioners and softeners - used to make the hair pliant and glossy after shampooing
- Fragrances to leave the hair with an attractive aromatic quality
- Sequestering - cleaning agents to remove specific minerals from "hard" water that may make cleansing more difficult
- Foaming agents which contribute little to a shampoo's cleansing power, but address the belief of consumers that "foam" or "lather" is necessary for effective cleansing.
- A growing market for "organic" products is represented in shampoos that use soap rather than detergent and add herbal extracts and vitamins to the list of ingredients.
- A number of anti-dandruff shampoos are available (see Dandruff). Anti-dandruff ingredients are zinc pyrithione (also called zinc omadine) and selenium sulfide. Which anti-dandruff shampoo will work best for any individual is difficult to predict; the consumer must usually decide on the basis of results. Excessively oily, scaly or itchy dandruff that persists may need medical attention.
When choosing a shampoo based on objective criteria, remember that hair is slightly acidic (see Hair Styling Products). Most shampoos are acidic to greater or lesser degree (pH of 5 is slightly acidic, pH of 3 is more acidic). The shampoo of greater acidity (lower pH) tends to have greater cleansing power-an attribute not needed by most people whose hair is not especially dirty or oily.
Another set of objective criteria is to identify the ingredient listed as a detergent. Detergents can be categorized into three chemical groups:
- Anionic-are considered cleansers that may need more post-shampoo conditioning. Detergents in this group include sodium lauryl sulfate, sodium laureth sulfate, TEA lauryl sulfate, ammonium laureth sulfate, ammonium laureth sulfite, DEA lauryl sulfate and sodium olefin sulfonate.
- Nonanionic-milder cleansing agents that leave the hair softer and glossier than an Anionic cleanser. Detergents in this group include polysorbates, nonoxynols and polyoxymers.
- Amphoterics-milder than Nonanionic cleansing agents, non-irritating to eyes, leave the hair soft and glossy. Detergents in this group include cocoamphotericglycinate, cocoamphopropionate and cocoamphocarboxyprionate. The amphoteric shampoos are sometimes called "baby shampoos". Persons with kinky hair generally should use shampoos that are mildly cleansing, with a pH of about 5. This type of shampoo is generally more effective in cleansing and "detangling" hair.