Emotional support animals, or ESAs, have exploded across the US in recent years, with rising numbers of pet owners getting their animals certified online. Unlike in the UK, ESAs have legal status in the US on a tier below traditional service animals, but the backlash has begun – with critics complaining the system is being abused by regular pet owners who want to take their animals into unsuitable public spaces. The Guardian's Richard Sprenger – animal lover but pet sceptic – meets ESA owners and their animals across North America.