Many "natural" shampoos are soap-based. You'll see the ingredient listed as "saponified oils" of almond, jojoba, olive, etc. Saponification is simply the process of adding sodium or potassium hydroxide - also known as lye or potash - to animal fats or vegetable oils. The result is an alkaline soap solution. On the chemist's pH scale, alkalis have numbers greater than 7, while acids have numbers less than 7.
Hair's pH
Hair is more on the acidic side, and has an ideal pH of 4.5 to 5.5. When a hair is placed in an alkaline solution (like water and baking soda), the cuticle cells swell and lift, leaving the hair with a rough, dull texture. When hair is placed in an acidic solution (water and lemon juice), the cuticle is sealed, leaving the hair smooth and shiny.
Bleaches, hair colors, permanents and relaxers are all alkaline solutions that lift the hair's cuticle to create the desired results.
Dulling Deposits
In addition to roughing up the cuticle, soap-based shampoos also leave mineral deposits behind, which is why hair can appear extra dull after weeks of use. That's why our great-grandmothers often followed their hair washings with a lemon or vinegar rinse - with a pH of 2, the acid rinses would reseal the hair's cuticle, which had been lifted by the alkaline soap.
Today's lab-created shampoos use surfactants to clean the hair. Common mild surfactants that wash away dirt and oil from hair but don't strip away the skin's natural oils are ammonium laureth sulphate and sodium laureth sulphate.
Natural Alternatives
If you still prefer to go "natural", look for shampoos containing cleansing agents such as soapwort (Saponaria Officinalis), soapbark (Quillaja Saponaria), and soapberry (Sapindus Indica). These ingredients will cleanse your hair without swelling the cuticle and causing damage.
