Abstract: A process for detecting previous treatment of keratinous fibers with alkaline technology for hair straightening or smoothing includes: bringing the keratinous fibers into contact with an extraction solution under conditions effective to cause dissolution of keratin proteins; and conducting a qualitative and/or quantitative assay of the keratin proteins dissolved in the extraction solution. The extraction solution may include a mixture of at least one of urea, thiourea and derivatives thereof with at least one reducing agent, and the at least one reducing agent may be free from thiourea. A kit for performing such a process is also provided.