They used to help my ex with her symptoms as soon as the drop (it is in liquid form) hit her tongue. Rescue Remedy is a popular product and is somewhat of an emergency use kind of thing, especially if you're in a panic attack mode and it has many of those "essences" in a combo. This site has the entire list, though some sites provide more or less information on the symptoms they relieve. Yes, they do work on pets and no there aren't any side effects (though yes, if you are worried then see a vet but be prepared to get confused looks). It is basically just like taking a vitamin your body is deficient in. The only negative I have noticed is that sometimes people can get addicted similar to how people get addicted to chap stick. If you're curious or worried, by all means do more research.
If I remember right, basically these "essences" are basically these flowers boiled into a tea, so instead of paying obscene amounts for a little dropper bottle it might be possible to buy the plant itself and make your own tea. I could be remembering wrong, but it wouldn't hurt to be surrounded by these plants I don't think (unless you're allergic). I personally have never been able to afford the bottles myself but I have tried them when I visited my ex. Basically tastes like water if you're worried about taste.
If you ever go to Whole Foods Market they have a display usually that has a chart with more info too.
Interesting that I would look at crab apple; I grew up loving the crab apple tree on my front lawn, and being the only one to eat its apples.
We have 3 crab apple trees in our front lawn. we usually turn the apples into jam.
