Not all allergies (or sensitivities/intolerances) will show up on an allergy test so I wouldn't go to a bunch of trouble for it now. You can figure this out yourself. (And I say that even though my two sons both see an allergist that we like very much. But he's nowhere close to you! ;)
Keep a food diary and try eliminating some stuff. Start with dairy since you already seem to have connected it to your hives. If your symptoms clear right up, you're all set! :) Yeah, avoiding dairy is a pain but so worth it if it makes everyone feel better. The 6 weeks someone mentioned is just a guideline. I did 3-week eliminations to figure out my DS2's intolerances...milk did take 4 to clear both me and him but most other foods I can tell a difference faster than that. One way I've heard to time it is pull the food 'til you get to 'baseline' (absence of symptoms) and remain there for 3 days. Then you can try to reintroduce & see if the symptoms return. If so, pull the food longterm.
I'm in a great allergy group on Yahoo (TerrificKidsWFA... we're also on Facebook but don't talk there much) and there are people in there who developed allergies in adulthood. After a pregnancy, surgery, avoiding a particular food for a while, or completely at random! So you may have developed a milk allergy, and it may or may not be related to your DD's.
Best of luck!