What is the definition of pus in Islamic law, and is the yellow substance that comes out of acne considered pus?

Pus is what comes out of a wound; it is pure exudate not mixed with blood, or a serous discharge that resembles water with traces of blood. The yellow substance that emerges from acne falls under the definition of pus. The ruling on pus and serous discharge is the same as that on blood, according to the majority of jurists.