Today my 6 year old daughter ask this Question. If germs are bad for health then why Allah created them?
I need to explain it to 6 year old kid. What could be the best answer?
Well, this is a tricky question for one principal reason: Germ Theory came into existence only in recent times and no writings, religious or otherwise, ever talked about germs before that. (In fact, the first person to suggest that doctors should wash their hands, namely Ignaz Semmelweis, was ridiculed and ended up in a nervous breakdown).
So there would be no Hadith or religious resource for any honest person to guide you.
Talking to a kid, the first thing to do is to ask him or her what he or she thinks. It is very important to let the kids meditate, think, and forge their own ideas. Once that is done, the way I explain it to my nephews is the same way I explain why there are black holes, and asteroids. And have you ever thought of snakes, and lions? There are a lot of dangers out there. Their mistake is thinking that "it is bad for us", as if "us" were the center of the universe.
The way I talk about this with kids is first by making sure they understand that, as human beings, their intelligence and superiority notwithstanding, they are part of a bigger world that they have to respect and learn about. One of my favorite verses is one that pushes to meditation:
“We will show them Our Signs in the universe, and in their own selves, until it becomes manifest to them that it is the truth” [Fussilat 41:53]
Nothing can bring you closer to God than to study His signs.
You can also explain to him that God put, in the very beginning of the universe, the whole potential of creation in a very condensed point which then expanded to yield the stars and the planets, and that God put in place the basic laws of physics and math, and from these laws, the laws of chemistry and biology, and from these, the very first unicellular organisms, which then evolved according to His laws to give the evolved being that he his. But the laws of God did not permit all of creation to evolve, and some of it stayed in the germ stage.
You can also tell him that a lot (in fact a huge amount) of unicellular organisms are essential to him, that of in his body there are more germ cells than human cells, that there are a lot of good germs and that they help defend his skin against the bad germs, and there are a lot of these inside his stomach and they help digest his food.
Germs, like any other part of the Creation, serve a purpose. And the only way for him to find this purpose, if he does not know it, is to study, and learn, and explore.
Allah created everything for a purpose, but excess or incorrect placement of anything can be dangerous.
E.g. water is amazing and life for us. However, if it enters your lungs, it does the opposite.
Similarly, fire is amazing, it helps us cook food so that we can eat and be healthy and living, it's helpful for life. But imagine the same fire surrounding the person, it does the opposite.
All these germs are part of some cycle. They help the ecosystem, are food of some other organisms while get rid of some others. But when they're in excess or in wrong place or manner, they harm us.
Our body consists of almost 2kg or so of bacteria only, and they're all fine and helpful. But if those just get slightly higher in quantity, we get sick. In fact if they get slightly less too, we will be ill.
Hope this answers the questions.