Rates of sexually transmitted infections (STI) in the UK continue to increase. A discrepancy between knowledge and awareness of STIs, and sexual behaviour appears to be ubiquitous throughout the world. We hypothesize that human beings are biologically programmed to fall in love and bond in powerful relationships, which, at least in the short term, prevents them from using knowledge and cognitive strategies to prevent STI acquisition. We compare this with obsessive thoughts and compulsive behaviours seen in obsessive-compulsive disorders. We suggest how romantic love might overwhelm logical thought processes to cause a deterministic and non-logical response to have sex and thus acquire STIs. An understanding of this concept may help us humans to be more insightful and thoughtful about STI acquisition.