It really depends on what ET life looks like. If it shares a common set of DNA for example then it would be much more likely that it could be dangerous. But if

It really depends on what ET life looks like. If it shares a common set of DNA for example then it would be much more likely that it could be dangerous. But if it’s not even Carbon based then it could be totally inert to us and vice versa. The biochemistry might literally prevent all interactions. We won’t know until we can examine it up close.