CUSTODIAN WAS DOING A CLEANING SUPPLIES INVENTORY. SHE HAD A BOTTLE OF DRINKING WATER SETTING ON THE SHELF NEXT TO THE CLEANING SUPPLIES. GRABBED A BOTTLE OF AIR FRESHENER INSTEAD OF WATER AND TOOK A DRINK BUT DID NOT SWALLOW. BOTH BOTTLES WERE CLEARLY LABELED. CHEMICALS IN AIR FRESHENER CAUSED IRRITATION TO GUMS.