Water
Washing in water alone, with agitation provided by hand or machine, will remove some loose dirt and particulate soils. Wetting or soaking in water softens some water-soluble soils, such as mud, making it easier to remove them.

However, water alone cannot remove soils that are not soluble in water. Such soils include automotive oils and greases; cooking fats, oils and greases; and body lipids, oils and perspiration that cause "ring around the collar" and underarm stains on shirt s. Neither can water alone remove colored stains, such as fruit juice, grass, blood, ketchup, etc. Water also has no sanitizing effect.

Furthermore, water does not have the ability to keep removed soils suspended. The removed soils are finely dispersed in the wash water and then redeposit onto the clothes. Redeposition of soils is the major cause of fabrics graying over repeated launderin gs.

Water Plus a Detergent
Detergent or, more specifically, the detergent surfactant, has the unique ability to remove both water-soluble and non-water-soluble soils. One end of the surfactant molecule (the lipophilic or oil-loving end) penetrates oily soils, while the opposite end of the molecule (the hydrophilic or water-loving end) solubilizes the oils. This action loosens soils and disperses them in the water.

Surfactants and other ingredients in laundry detergents also work to keep the removed soils suspended in the wash water so they don't redeposit onto the cleaned fabrics. This prevents graying of fabrics. Other laundry detergent ingredients, such as enzyme s and bleach, work to remove colored stains.

Detergents are effective at washing away many germs. Sodium hypochlorite (chlorine) bleach remains the most effective way to sanitize laundry where germs and bacteria are a concern, such as with diapers or when there is illness in the home.