After catching a virus on an airplane nine years ago, Chrissi Kelly lost her sense of smell. To cope, she began smell training, a therapy that involves repeatedly sniffing potent odors as a means to stimulate the olfactory cortex, the part of our brains responsible for processing and perceiving scents. The little-known technique, first described in a research paper by a team of German experts in 2009, paired with the lack of resources available to help people with olfactory deprivation, intrigued Kelly. She dove into more scientific research about smell loss, and soon developed her own smell training kits and the companion Snif app, both available via AbScent, a British nonprofit she founded in 2018 that’s overseen by an advisory board of leading doctors and scholars.