According NewScientist, the DNA from a man's saliva can be detected in the saliva of a woman he kissed up to an hour after the kiss occurred. This was revealed by a study that was conducted at Comenius University in Slovakia.
According to the study, the saliva was detected by finding a Y chromosome, which means that this method can only be used to identify male DNA in female saliva after a kiss is exchanged. NewScientist states that the saliva samples collected for analysis were taken after the couples had kissed "passionately" for a minimum of two minutes. The women's saliva was collected at a maximum interval of 50 minutes, leaving open the possibility of the male DNA surviving in a woman's for more than an hour after a kiss.