Ichthamol (Ammonium bituminosulfonate) is an old and popular equine (and human) remedy that is often applied to the hoof for hoof infections. It is chemically a “sulfonated shale oil” and is formed as a distillate of oil shale. The commercial ointments typically contain lanolin and a variety of other ingredients.
I always heard that Ichthammol is a “drawing salve”, meaning that it supposedly “draws out infections”. In fact, it is more likely that it simply softens overlying skin or hoof, allowing infections to more easily break through the tissue to drain. It is also purported to have anti-inflammatory and limited antibiotic activity. It is apparently used in humans for ear infections. Above all, studies have shown it to be generally safe in humans, and so it is likely safe as it is used in horses.
I have seen Ichthammol used on snake bites and insect stings, pigeon fever abscesses, infected jugular veins, and inflammatory skin disorders. It seems somewhat helpful in my experience but not miraculous. I have clients who have claimed that they have used it or pine tar to “draw out” fragments of bone or foreign bodies. It likely is not effective for this purpose.