If the biology is different enough, things like viruses wouldn’t easily cross between the planets. But bacteria could still probably exploit us (and them), and nothing would stop things with claws, teeth, and spikes from hurting us even if they couldn’t ultimately digest us.
Even if the alien species had completely incompatible biology (no DNA or RNA), a human body is still a warm habitat that contains water and useful minerals. So something small would probably settle inside of us.
And our immune system couldn’t interact with it and therefore not kill it.
If the biology is different enough, things like viruses wouldn’t easily cross between the planets. But bacteria could still probably exploit us (and them), and nothing would stop things with claws, teeth, and spikes from hurting us even if they couldn’t ultimately digest us.
Even if the alien species had completely incompatible biology (no DNA or RNA), a human body is still a warm habitat that contains water and useful minerals. So something small would probably settle inside of us.
And our immune system couldn’t interact with it and therefore not kill it.
Ah, drat! My one weakness! Claws! Oh, and teeth. So two weaknesses.
Oh, and spikes.
Oh, and fire.
Pointed rocks.
Long falls off of cliffs.
Ok, I have many weaknesses!
https://www.youtube.com/watch?v=LD6nxu8cNIA