TMZ has learned ... Loc was attending a charity event to benefit "My Friend's House" -- which provides food to homeless people -- when he began to flail around in his seat.

Witnesses tell us ... Loc fell to the floor and was "gasping to breath" ... as friends wiped the sweat from his head and cooled him off with cold water.

Someone called for an ambulance ... but we're told Loc recovered quickly ... so the ambulance was canceled.

Sources say Loc left the event immediately following the medical scare ... and we're told he's at home resting.

As TMZ previously reported, Loc told police he suffers from seizures after he was pulled over for DUI last year.

Still, Tone's manager insists Tone did NOT suffer a seizure last night ... telling us Tone merely got sick from bad food.