Spice e/o's speed up trace - clove bud, ginger, etc. I alway add them at the very last minute.
Rose geranium seems too as well.
I also find using mica can speed things up a bit. Not discounting water can help.
Lavender seems to actually put trace back. I find I will have to stir for a bit longer after adding this one.
I find that most e/o's are easy to work with in that department. Fragrance oils tend to be more tempermental but have a much grater range of scent. Especially foody smells. And they are on average much cheaper.
I use e/o's more because of allergies .... many fragrance oils will give me headaches and make me sneeze.
The Scent Review Board some information ib EOs as well as FOs. You will need to register before you can view. Then scroll down... down... down... and eventually you will find it.
I second where carebear directed you too, it is a very resourceful site. Any good, reputable seller of either EO's or FO's, should in their scent description, tell you whether the scent accelerates trace, seizes, or turns the soap a much different colour.
Guess it just depends on what you're allergic too. I must be allergic to some of the ingredients in Fo's. I used to use them alot and love them. Now I try to limit my exposure. I loved Masculine Musk by Sweetcakes but oh my - instant headache.
Everyone is different. In my time candlemaking and soaping I've come across as many people who tell me they have problems with FOs as with EOs. It's an interesting world.
There are some almost universal fragrance chemicals that perfumers work with, plus some very common solvents, so perhaps its one (or some) of these that you are sensitive to.