Cream of tartar is also known by its chemical compound name, potassium bitartrate. It is an acid salt found in the bottom of wine barrels after fermentation has occurred. While useful in cooking as a thickening agent, the chemical carries a mild to moderate risk of health hazard if it contacts the eyes or skin or is ingested in large quantities. This is definitely one of those ingredients to keep on a high shelf and out of the reach of small children who may unknowingly ingest the chemical.
Eye Irritant
Cream of tartar carries an NFPA rating of 2, making it a hazardous chemical. This means it may potentially cause mild to moderate eye irritation such as redness and swelling if it contacts the eye directly. Those affected should remove their contact lenses, if any are being worn, and flush the eyes with plenty of water for 15 minutes.
Skin Damage
The NFPA also gives cream of tartar a fire hazard rating of 1, which translates to the compound's being an explosion risk at temperatures over 200 degrees Fahrenheit. Below this temperature cream of tartar may still cause mild to moderate skin irritation because of its acidic properties. Those who experience this are instructed to wash the affected area with soap and water, then cover it with a skin moisturizer.
Inhalation and Ingestion
Inhalation and ingestion of small amounts of cream of tartar may cause mild to moderate nausea. Toxicity (stomach cramping, dizziness, difficulty breathing) may occur if larger amounts are ingested or inhaled. If you inhale or ingest cream of tartar, get fresh air and contact a medical health professional. Do not induce vomiting unless directed to do so by medical personnel.