When I was a teenager I worked in the local drugstore. A lady came in and bought a package of hemmohroid suppositories (I can't remember if it was Preparation H) and remarked that they were the nastiest things she had ever tasted but they sure worked good. We asked her how she was taking them - yes, she was swallowing them. Hadn't bothered to read the directions.

Once my dad burned his hands (steam) and the pharmacist recommended Preparation H to take the sting away.

I don't think it's harmful even if swallowed.