Factually, we know that soap has been around for about 2,800 years.  The earliest known evidence of soap use are Babylonian clay cylinders dating from 2800 BC containing a soap-like substance. A formula for soap consisting of water, alkali and cassia oil was written on a Babylonian clay tablet around 2200 BC.

The Ebers papyrus (Egypt, 1550 BC) indicates that ancient Egyptians bathed regularly and combined animal and vegetable oils with alkaline salts to create a soap-like substance. Egyptian documents mention that a soap-like substance was used in the preparation of wool for weaving.

According to Pliny the Elder, the Phoenicians prepared it from goat’s tallow and wood ashes in 600 BC and sometimes used it as an article of barter with the Gauls.   The word “soap” appears first in a European language in Pliny the Elder’s Historia Naturalis, which discusses the manufacture of soap from tallow and ashes, but the only use he mentions for it is as a pomade for hair; he mentions rather disapprovingly that among the Gauls and Germans, men are likelier to use it than women

Soap was widely known in the Roman Empire; whether the Romans learned its use and manufacture from ancient Mediterranean peoples or from the Celts, inhabitants of Britannia, is not known.  Early Romans made soaps in the first century A.D. from urine to make a soaplike substance.  The urine contained ammonium carbonate which reacted with the oils and fat in wool for a partial saponification.  People called fullones walked the city streets collecting urine to sell to the soapmakers.

The Celts, who produced their soap from animal fats and plant ashes, named the product saipo, from which the word soap is derived. The importance of soap for washing and cleaning was apparently not recognized until the 2nd century A.D. ; the Greek physician Galen mentions it as a medicament and as a means of cleansing the body. Previously soap had been used as medicine.

The writings attributed to the 8th-century Arab savant Jabir ibn Hayyan (Geber) repeatedly mention soap as a cleansing agent. The Arabs made the soap from vegetable oil as olive oil or some aromatic oils such as thyme oil. Sodium Lye (Al-Soda Al-Kawia) NaOH was used for the first time and the formula hasn’t changed from the current soap sold in the market. From the beginning of the 7th century soap was produced in Nablus (Palestine), Kufa (Iraq) and Basra (Iraq). Arabian Soap was perfumed and colored, some of the soaps were liquid and others were hard. They also had special soap for shaving. It was commercially sold for 3 Dirhams (0.3 Dinars) a piece in 981 AD.

Soap in the Middle Ages

    Historically, soap was made by mixing animal fats with lye. Because of the caustic lye, this was a dangerous procedure (perhaps more dangerous than any present-day home activities) which could result in serious chemical burns or even blindness. Before commercially-produced lye was commonplace, it was produced at home for soap making from the ashes of a wood fire.

In Europe, soap production in the Middle Ages centered first at Marseilles, later at Genoa, then at Venice. Although some soap manufacture developed in Germany, the substance was so little used in central Europe that a box of soap presented to the Duchess of Juelich in 1549 caused a sensation. As late as 1672, when a German, A. Leo, sent Lady von Schleinitz a parcel containing soap from Italy, he accompanied it with a detailed description of how to use the mysterious product.

Castile soap, made entirely from olive oil, was produced in the Kingdom of Castile in Europe as early as the 16th century (about 1616).   Fine sifted alkaline ash of the Salsola species of thistle, called barilla, was boiled with locally available olive oil, instead of tallow. By adding salty brine to the boiled liquor, the soap was made to float to the surface, where it could be skimmed off by the soap-boiler, leaving the excess lye and impurities to settle out.  This produced what was probably the first white hard soap, which hardened further as it was aged, without losing its whiteness, forming jabon de Castila, which eventually became the generic name.