Ruling 215. If the body of an animal becomes impure with an intrinsic impurity like blood, or with something that has become impure, such as impure water, in the event that the impurity is removed, the animal's body becomes pure. Similarly, the inner parts of a human body – like the inside of the mouth, nose, and ears – become impure by coming into contact with an external impurity, but by removing the impurity they become pure. As for internal impurity – such as blood that comes out from in between the teeth – this does not cause the inner parts of the body to become impure. Similarly, if an external object inside the body comes into contact with internal impurity, it does not make the object impure. Therefore, if dentures come into contact with blood that comes out from in between the teeth, it is not necessary to wash the dentures; but if the dentures come into contact with impure food, it is necessary to wash them.

Ruling 216. If some food has remained between the teeth and blood comes in the mouth, the food does not become impure by coming into contact with the blood.

Ruling 217. Those parts of the lips and eyelids that overlap when shut are ruled to be inner parts of the body. Therefore, in the event that they come into contact with some external impurity, it is not necessary to wash them with water.[1] However, with regard to those parts that one does not know whether they are outer or inner parts of the body, it is necessary to wash them if they come into contact with external impurity.

Ruling 218. If impure dust settles on dry clothing, a carpet, or similar thing, in the event that the object is shaken in a way that the amount of dust that is certain to have been impure falls off, the clothing, carpet, or similar thing is pure and it is not necessary to wash it.