The first point which should be considered is that uncleanliness in Islam is a concept opposed to cleanliness and purity; not a concept which something is considered as worthless or bad.
Dogs are considered more than other animals by humans because of loyalty and obedience. Dogs are among the many creatures of God and in Islam all creatures are considered as having worth and some rights are considered for them. Islam is the only religion which has mentioned particular rights for some animals and has obliged humans to observe them.
From the beginning, dogs have had roles as the herd guards or the guards of properties as houses and farms and Islam does not have a problem with this. The only point is that dogs should not enter the living place of humans; and this has logical reasons in which the benefits for humans have been considered.
Overall, dogs can be harmful from two aspects, physical and psychological. From physical aspect, dogs can cause various illnesses which often can cause death for humans. As proved in tests, a worm lives in the digestive system of dogs which is excreted in the excrement of dogs or its seeds or itself gets out and if they enter the digestive system of humans they can cause very dangerous illnesses. Also, dangerous sicknesses like rabies which exist in the saliva can cause the death of the person.
It may be said that what the roles of vaccines, detergents and drugs taken for dogs are?
These may prevent the transfer of some diseases to some extent, however, they do not change the digestive system of dogs and the parasite living in dogs.
Dogs can be also harmful to humans from psychological aspects. It was mentioned above that dogs can create attachment between themselves and the owner due to their loyalty and obedience. Maybe, it seems pleasant at first, but it has been proved by experience that getting into the habit of being with animals like dogs, distances humans from the mood of communicating with humans.
It is not unknown to anyone that dogs have a special position as a family member in the west, marriage and children are ranked next. It is correct that reduction in the number of children and marriages have various factors; yet, living with animals in particular with dogs, is one of the noticeable topics in a way that the famous animation was made in this regard titled “Baby Boss” which deals with keeping dogs and a decrease in the tendency to have children.
However, there is a third point which fewer people pay heed to. When you enter animals into your living place, in the first place, you have distanced it from its habitat where it feels more comfortable in. The claws of animals are created to walk on soil and grass not for walking on carpets and ceramics! Certainly this reduces from their sense of comfort.
Dogs have a sharp sense of smell so some smells can be very displeasing to them. The smells which exist in the lives of humans such as the odor of the drain or some cooked or fried food.
Dogs reproduce and die naturally in the nature which keeps their population in balance. But, with humans’ interruption in the cycle and the increase in the population of dogs, nature faces damages and even the cycle of nature and this affects the population growth of other animals in a negative way.
On the other hand there are some self-seeking people who perform some genetic changes in dogs and dog-like animals to earn money and merely for the sake of pleasure for humans. What wrong has the poor animal done to be sacrificed for humans’ greed and pleasure seeking feature?
Regarding the fact that all Islamic rules are applicable in all ages and the expediency of societies and prudence have been considered, therefore, considering dogs as unclean is not because they are inferior creatures but from preventing humans to enter them in their lives and keep a border in between and not contracting physical diseases as well as prioritizing the topics which were addressed above, it is in the favor of humans and the dogs also not to be instruments to humans.