The present invention includes a hair straightening formulation consisting of a hair fixative that will straighten the hair for at least 2-3 months after one application despite frequent washings of the hair as well as methods for obtaining said formulation. The formulation comprises as active ingredients one or more keratin hydrolysates and an aldehyde. Hair straightening system comprising shampoo and one or more conditioners are also provided. The invention is further directed to a method for straightening hair using said formulation.