A method for assessing whether a drug of abuse and/or a metabolite of a drug of abuse is present in a keratin material, wherein said drug of abuse is selected from the group consisting of: amphetamine; barbiturate drugs; benzodiazepines; buprenorphine; cocaine; cotinine; EDDP; phencyclidine; ketamine; marijuana; methadone; methamphetamine; opiates; oxycodone; propoxyphene, said method comprising: - a step of extracting said drug of abuse and/or said metabolite from said keratin material, said step of extracting comprising: - prearranging an amount of said keratin material; - prearranging an amount of an extraction composition containing urea, wherein said extraction composition comprises an aqueous solution of urea at a predetermined urea concentration and at a predetermined pH wherein said predetermined urea concentration is set between 0.1 mol/litre and 3.0 mol/litre; - bringing said amount of said keratin material into contact with said amount of said extraction composition, obtaining an extract containing said drug of abuse and/or said metabolite; - a step of analysing said extract by an antigen-antibody technique comprising: - performing a reaction of said drug of abuse and/or said metabolite, which acts as an antigen, with a specific antibody; - detecting said antigen-antibody reaction, wherein said reaction of said drug of abuse and/or of said metabolite with said specific antibody is a first reaction, and the method comprises a step of comparing said first reaction with a second reaction between said antibody and a reference antigen for said drug of abuse and/or for said metabolite, wherein said reference antigen is a marked antigen adapted to produce a visually detectable chromophore compound in said second reaction with said antibody, and wherein said reference antigen and said specific antibody are arranged on a respective strip portion of an immunochromatographic quick test device. - a step of extracting said drug of abuse and/or said metabolite from said keratin material, said step of extracting comprising: - prearranging an amount of said keratin material; - prearranging an amount of an extraction composition containing urea, wherein said extraction composition comprises an aqueous solution of urea at a predetermined urea concentration and at a predetermined pH wherein said predetermined urea concentration is set between 0.1 mol/litre and 3.0 mol/litre; - bringing said amount of said keratin material into contact with said amount of said extraction composition, obtaining an extract containing said drug of abuse and/or said metabolite; - prearranging an amount of said keratin material; - prearranging an amount of an extraction composition containing urea, wherein said extraction composition comprises an aqueous solution of urea at a predetermined urea concentration and at a predetermined pH wherein said predetermined urea concentration is set between 0.1 mol/litre and 3.0 mol/litre; - bringing said amount of said keratin material into contact with said amount of said extraction composition, obtaining an extract containing said drug of abuse and/or said metabolite; - a step of analysing said extract by an antigen-antibody technique comprising: - performing a reaction of said drug of abuse and/or said metabolite, which acts as an antigen, with a specific antibody; - detecting said antigen-antibody reaction, - performing a reaction of said drug of abuse and/or said metabolite, which acts as an antigen, with a specific antibody; - detecting said antigen-antibody reaction,