Zimmermann reagent consists mostly of toxic chemicals. Keep out of eyes and mouth. Keep away from children. Always use in a well-ventilated area. Wear gloves (supplied) when handling the bottle and cap. Wear protective eyewear. Never point towards face etc. If you get some on you/clothing, then immediately wash with soap and water. Wash testing surfaces with soap and water as well. Dispose of any unwanted reagent down the sink with running water, ventilate. Store all testing kits away from any heat in a cool, dark place between uses. The average shelf life of 1 year can be significantly extended by storing in a freezer (warm to room temperature before use).
A positive or negative reaction for a substance does not indicate if it is safe. No substance is 100% safe.