Abu-Horaira said that the Prophet peace be upon him said: (To purify one's vessel licked by a dog, he should wash it seven times, the first time is with dust) and Abu-Horaira said that the Prophet also said: (If a dog licked in one's vessel, he should clear it then washes it seven times) [Narrated by Muslim].

Scientists have revealed a strange fact which is the presence of an antiseptic substance in dust. When the scientists studied the composition of dust, they have found that it contains substances that if mixed with bacteria and germs, they overcome them immediately and that the dog's saliva contains pathogens for humans that couldn't be cleaned except by dust…….

So Glory to Allah the almighty !