Oxalic acid is a naturally occurring organic compound found in many plants, including leafy greens like spinach and kale. It is a colorless, crystalline substance that can form salts known as oxalates. In small amounts, oxalic acid is generally safe for consumption, but high levels can be harmful and may lead to kidney stones in susceptible individuals. In addition to its presence in food, oxalic acid is used in various industrial applications, such as cleaning agents and rust removers. It can also be found in some household products. Due to its acidic nature, it is important to handle oxalic acid with care to avoid skin irritation or other adverse effects.