What ingredient should not be used on someone with an iodine allergy?

The correct choice is algae because certain types of algae, particularly seaweeds, can contain significant amounts of iodine. Iodine is a key component in many forms of algae, and using these products can pose a risk to individuals with an iodine allergy, as their bodies may react negatively to the iodine present. It’s crucial for individuals with such allergies to avoid any ingredient that could introduce iodine into their system.

In contrast, the other options—charcoal, aloe vera, and honey—do not typically contain iodine or have any relation to iodine in terms of allergy responses. Charcoal is often used for its absorbent properties and does not have iodine as an ingredient. Aloe vera is known for its soothing properties without any iodine content. Honey is a natural sweetener and has no relation to iodine. Therefore, avoiding algae is essential for anyone with an iodine allergy to prevent potential allergic reactions.