Borax is marketed as a green product because it doesn’t contain phosphates or chlorine. Instead, its main ingredient is sodium tetraborate, a naturally occurring mineral. While borax may be natural, that doesn’t mean it’s completely safe. Borax often comes in a box with a caution label warning users that the product is an eye irritant and may be harmful if swallowed. While people are mostly exposed to borax in their homes, they may also encounter it at work, such as in factories or at borax mining and refining plants.