Scientists identify ‘trigger molecule’ for Covid-related changes to smell

Scientists have identified the “trigger molecule” that makes pleasant aromas smell like burning rubbish or sewage in people whose sense of smell is disrupted by Covid. The loss of smell is a defining symptom of Covid-19, with about 18% of adults in the UK estimated to have been affected. Some people also experience disturbances in their sense of smell – a condition known as parosmia – but the biological basis for this has remained a mystery. Now scientists have identified a highly potent odour molecule that appears to be a trigger for the sense of disgust experienced by many of those with parosmia. The molecule, called 2-furanmethanethiol, found in coffee, was described by those with a normal sense of smell as being coffee- or popcorn-like, but those with parosmia typically described its scent as disgusting, repulsive or dirty.