How do some pears have a layer of oil on their surfaces?

It is a thin layer of wax coated on the surface of fruit, which is mostly used for gift fruit, in order to make the fruit more shiny. Wax similar to birthday cake is harmless to the body, but it is better to wash it off as much as possible. There is also a dirty one, which generally does not appear on gift fruits. It is left after rain and pesticide spraying. So try to wash the fruit with detergent repeatedly. If you can't make sure they are cleaned, peel them off. Health is very important. I usually use Amway detergent. Personally, I think it's good and clean.