Washing soda, which contains 100 percent sodium carbonate, should never be used as a substitute for baking soda, which contains 100 percent sodium bicarbonate. While both sodas can be used for laundry and cleaning purposes, sodium carbonate is a poisonous chemical that is not safe for human consumption.
To prevent accidental ingestion of washing soda, store it away from all food items in a clearly marked package. Sodium carbonate ingestion can cause symptoms like difficulty with breathing and swallowing, fainting, eye and skin irritation, vomiting, diarrhea, a rapid drop in blood pressure, and severe pain in the mouth, throat, chest and abdomen. Sodium bicarbonate is commonly used in household cleaners and is used in the production of glass and paper products.