Early soaps were adequate cleansers and fully biodegradable despite a lack of skin-friendliness. The process of making soap, saponification, is the breakdown of fat by a base into glycerol and three molecules of a fatty acid salt, or soap. The fatty acid salt, usally a sodium or potassium salt, has a lipid loving tail and a hydrophilic head. The lipophilic tail attaches to oils and fats on the skin and disperses it into the surrounding water. Soaps are emulsifying agents that allow the dispersion of an insoluble substance within water.
Most soaps are alkaline and unless pH balanced can cause skin irritation if used excessively.
Routine hand washing is most effective in removing bacteria and other microorganisms from the skin. Antibacterial agents are sometimes added to soaps and may decrease body odor by inhibiting bacterial action on apocrine sweat . As surfactants, soaps decrease surface tensions in liquids and therefore allow the formation of soap bubbles and lather. Mildness, biodegradability, low toxicity, cleansing ability, emulsification, moisturization, skin appearance and feel and lubrication are all important aspects of soap performance. Surfactants vary in biodegradability and some synthetic forms have caused large fish kills in the recent past.