Yes, allergy testing was worth it. Our son was tested for various allergies at age 20 months, after a severe allergic reaction. In addition to a severe allergy to peanuts, he is also allergic to dogs and cats (and we have 2 dogs).
Anyway, typically, then do "scratch tests" were a very small amount of the allergen is pricked into the skin. They do it in sets of 6 (or maybe 8) at a time, and do a bunch in a row. They'll probably test for food and environmental allergies. Some of the spots they will circle with a pen (I'm not sure why). They will wait about 15 or 20 minutes, then the doc will come in and read the results.
This will help you to find out what sorts of things you should trying to avoid, and also what things you can try to do to manage his systems and flare ups.
According to both the pediatrician & allergist, the congestion that comes from allergies can actually end up being a major culprit in ear infections. That, plus the snoring cause by the congestion and that our little guy seemed tired all the time (because he wasn't sleeping well due to the congestion/snoring) caused us to go ahead and decide to give medication. He's been on Singulair and is currently on Zyrtec. We have noticed a difference.