Avon and Somerset Police said 10 people, including the boy, complained of stinging or itchy eyes and skin, but ‘responded well to treatment’ at the scene.
The store was evacuated while the incident was investigated, and a boy was arrested on suspicion of attempting to cause grievous bodily harm and administering a noxious substance.
The liquid is believed to be a type of home-made chilli spray with no strong acid or alkaline ingredients and was ‘found to be unharmful’, Avon Fire and Rescue Service said.
One shopper said: ‘There was a chemical attack on someone and the police were treating it as a terrorist attack.
Police were called to the superstore in Avonmouth at around 6.30pm on Monday following reports of a chemical incident.
