The rule concerning internal and external usage

If anything is impure in itself, such as excreta, urine, alcohol, an animal that has died a natural death, pork, etc. then it is not permissible to use such items internally or externally. As for things which have become impure on account of their being mixed with other impure substances, the ruling is that they cannot be used internally. However, it is permissible to use them externally. Such substances are: impure water (pure water which became impure on account of an impure substance falling into it), liquid of the bladder that is added in surmah (as long as this liquid is not more than the other ingredients), medicines that contain alcohol as long as the alcohol content is less than the other substances. However, it should be borne in mind that it is necessary to wash off these substances and purify oneself prior to offering salaat . Although it is permissible to use such substances externally, it is preferable to abstain from using them. The reason for this is that when a person is very sick he is not very mindful. There is a great possibility of such substances falling onto his clothing. Furthermore, if the person did not wash his hands after applying such substances, and his hands come into contact with water in a utensil, then the utensil and the water will be rendered impure. In this way, this impurity will affect the entire house and many persons' salaat will be ruined.

When we say that a substance becomes impure on account of it being mixed with an impure substance, we mean that the impure substance is not more than the other substance. If it is more, it would be considered as if the entire mixture comprises of the impure substance. For example, if a handful of water is poured into a large utensil containing urine, we cannot say that this is water. By the water being mixed with the urine, it has now become impure. In fact, this entire mixture will be considered to be urine (and the rules that normally apply to urine will apply over here as well). But if the opposite takes place (i.e. if a handful of urine is poured into a large utensil containing water), then the opposite ruling will also be given (i.e. the entire mixture will be considered to be water - although the water itself will be regarded as impure). It should be also known that in our pure Shariah , prohibition in using a particular thing or substance is based on four reasons: (i) on account of the thing being najis (impure), e.g. urine, excreta, etc. (ii) on account of the thing being harmful, e.g. poisonous substances, (iii) on the basis of istikhbaath , i.e. things that are abhorred and disliked by a normal person possessing a sound mind, e.g. worms, certain insects, etc., (iv) on account of the thing causing intoxication.