Love riddles with simple answers

What is invisible and makes people suffer from symptoms like sweating and nausea, yet people can’t survive without it?

Which one of Santa's reindeer can be seen on Valentines day?

He has married many but has never been married . Who is he?

What three words are said too much, yet not enough?

What do squirrels give each other for Valentine’s Day?

What do you call two birds in love?

It caused the destruction of Troy, The worst of tragedies, And numerous maladies, Yet it is chased, desired and fought for. What is it?

It's Valentine's Day! What reindeer do we see on this day?

What makes grown men cry, but humanity would go extinct without it?

This word is a favorite of girls. Boys are unnerved on the mention of it. Once love finds its accompaniment, it becomes a lifelong event. What is it?