Why do pools of blood hurt you in Doom?

Going by canon and not technical details, I understand the nukeage texture can stand for radioactive waste and plain old toxic waste, and the two cooling lava textures can be blood covering a rocky floor like in the Cyberdemon room in Tricks and Traps. But why would any animal's blood (including humans) harm someone?

I don't mean diseases but the liquid itself assuming it's not transfused. Did the demons pour acid into the pools and streams when their bosses weren't looking? Or do they get heated up when passing through the cooling lava pools?

Hmm, maybe some types of demon blood is Really acidic

And yet Flynn eats them when you Fatality someone in Brutal Doom. (explaining the health bonus for fatalities)

Yeah, but Brutal Doom isn't canon, but a fan-made mod.

Even so...

In Project Brutality you can get Cruelty bonuses So I'm thinking his health is partly based on morale/ego in that mod or the "Demon strength" rune could be somewhat sated by the destruction that Taggart can cause.

Maybe it's boiling, or acidic, or whatever -- large pools of blood should coagulate after all. Maybe there are tiny biting demonic bugs swimming in it and they nibble on Doomguy. Maybe the blood is radioactive.

Come to think of it, those broken strobe lights in some floors of E2M2 and E2M7 might actually be the remains of the monorail system from Tom Hall's original Alpha.

EDIT: I'd quite like to see someone make a Brutal Doom compatible mod done Half Life 2: Missing Information style, with help from Tom himself to try and show us what Doom would look like if Tom had his way.

A couple of the characters ended up in ROTT so their appearance could be an Alternate reality cameo from that game plus their 2013 voices (If id Tech 1;s modern versions can handle it.)

Thing that bothers me most about Brutal Doom is how the zombies scream in pain clutching their severed limbs.

Zombies.

In pain.

But they aren't your usual zombies as they have enough brainpower to use their weapons, so I see no reason that they wouldn't feel pain.

To me they seem more like possessed humans than your classic zombies.

Doom 3 kind of solidified the undead angle for me. Yeah its a remake of one but it kind of shows the original design of the zombies. Even the fast gun using zombies, while flailing from gunfire, do not scream in pain over it. They are simply reacting to the physical force of the bullets striking their bodies.

While they do make pain noises in the originals hinting at partially still being human... it just looks ridiculous having them grabbing limbs in pain. I'd much rather see them immediately go to the animation where they pull out a pistol if you take off a leg than have them flail around for 30 seconds.

Like deadites ;)