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.
