Agave is from the agave plant (cactus or succlent family). Is used in an alcoholic drink as well & some people are allergic to it. You can use less of it than you would the other sweetners. That is the extent of my knowledge on agave.
I think agave is fine. Read the label carefully though-some are highly processed. I didn't think it was a high allergy risk. It's recommended for the Clean diet where all common allergens, sugar and caffeine are avoided.
Re: Agave?
I'd rather use sugar and just use very little.
https://www.webmd.com/diet/features/the-truth-about-agave