Keratin-based hair straightening formulations, methods and systems

A method for straightening a quantity of curly or frizzy hair, comprising:

• contacting the quantity of curly or frizzy hair with a hair straightening composition, wherein said hair straightening composition comprises;
• (1) one or more organic acids selected from the group consisting of formic acid, acetic acid, propionic acid, tartaric acid, adipic acid, succinic acid, ascorbic acid, malonic acid, oxalic acid, pyruvic acid, picolinic acid, dipicolinic acid, citric acid, and combinations thereof;
• (2) a keratin lysate;
• and
• (3) one or more reducing agents selected from the group consisting of members of the thiazoline family, members of the 2-mercapto-ethane family, dithiothreitol (DTT), sulfamic acid, and combinations thereof, wherein (a) one or more of the organic acids reduce the pH of the hair straightening composition to a range from greater than or equal to 2.45 to less than 4.0, (b) one or more organic acids of the hair straightening composition reduce disulfide bonds of a curly or frizzy hair contacted with the hair straightening composition, and (c) the curly or frizzy hair maintains a straight configuration for at least two months after it has been heated and mechanically straightened before reverting to the natural curl configuration;
• heating the curly or frizzy hair to a temperature between about 150° C. and 235° C.;
• and
• mechanically straightening the curly or frizzy hair that is in contact with the hair straightening composition, so as to straighten the quantity of curly or frizzy hair,
• wherein the hair straightening composition is substantially free of formaldehyde, monofunctional aldehydes, dialdehydes, polyfunctional aldehydes, ketoaldehydes or chemicals that release formaldehyde upon heating.