One quick question

Both should be correct, the first one seems better to me.

"This saliva is what makes your skin swell up and itchy."

Usually we just say "swell up" not "swells up" in this sentence.

I hope I helped.

Thanks for correcting me!That is very helpful

I was just wondering, isn't saliva the watery substance produced in our mouth!?

And, I am confused with the determiner

Humans and other animals have saliva, not all the same.

I'm not sure if Preciousbunny wants to say "This saliva...." or just "Saliva", both are correct, but it depends on the context/situation.

"This saliva..." is referring specifically, whereas "Saliva..." is general.

I understand the grammatical difference.

What confuses me is that the sentence looks like a definition of saliva:

This saliva is what makes your skin swell up and itchy.

And, if so, why would saliva make your skin itchy, or even swell up? I think I miss some part of the meaning of saliva. If saliva is what I think it is, it doesn't make you skin itchy and, first

Saliva is as you understand. But what we don't know is in what context the sentence has been used in, she only put up the sentence, so it's hard for us to fully understand,

If it is a reaction then saliva could be the cause for itching.

For example: "The medicial examination reveals that this saliva is what makes your skin swell..."

We can not be sure of it's mean

Thank you.