These are very good questions, as it is important to make sure that cosmetics or any other applied product don't have a negative effect on your health. Initially, if you have concerns about your skin, the best person to talk to would be a dermatologist
. He or she can go over warning signs as well as suggest products that might be better for those with sensitive skin. In general, eye makeup sold in the United States has been tested to make sure that is safe to apply directly near the eye, but you are correct that any makeup does contain chemicals that can harm the skin. The best way to know that a product is causing a problem is stopping its use if you develop any skin irritation after applying them. Some brands of makeup are marketed as being more "natural" or "safer" for the skin, but you can only tell what will work for you by trying them. In any case, it is always important to use products as recommended and not apply them in a way that was not intended. Please talk to your dermatologist regarding any problem you develop. This is the safest way to find a product you can wear and enjoy with confidence.