Contrary to what the term might think shampoo it is not a word of English origin.
In fact, etymologically it derives from the Hindi “ chāmpo ” (imperative of champnā, i.e. 'massage'), which in turn originates from the Sanskrit “ cap ”, 'massage' indeed.
Around the second half of the eighteenth century, in the midst of the colonial campaigns of Great Britain in India, when a "shampoo" was offered, it was therefore referred to as a scalp massage.
Of course, decades have passed before we came to associate the term "shampoo" with the foaming detergent that we all know; to then use the English term in Italy it will be necessary to wait for the 30s of the last century.
Characteristic of the shampoo is naturally the foam, which is formed with the union of the air bubbles with the diluted detergent; the mechanical "work" of the massage, that is, causes air and liquid to be incorporated, generating foam, the quantity of which varies according to the product.
In fact, not all shampoos make a lot of foam, and the characteristic of organic products is precisely that of not producing excess foam.
In reality, it is the cleansing agents (or "surfactants") that perform the function of cleaning the scalp, therefore using bio-based products effectively implies the production of less foam but greater safety for the skin and less environmental pollution.