Sure sounds like an allergic reaction - of course to us non-doctors. Eating too fast might upset your stomach, but I wouldn't expect mouth numbness. You did right taking the antihistamine.
So seeing an allergist and getting skin testing is a good idea. But you can also do some simple testing at home, but only if you don't have any throat closing symptoms.
First thing to do is start a food journal. See many posts and threads in the archives - the search box at the top of the page. I like a medium/small notebook or a daily page calendar. Write the date, time and everything you eat and drink. Then write any reactions any time that day.
It can take anywhere from seconds or minutes to hours or even up to 2 days for food intolerances to trigger a reaction. It depends on the type of reaction, whether it's an allergy or "just" an intolerance. My allergist calls them all allergies.
FOOD CHALLENGE - DO NOT DO THIS IF YOU HAVE A SERIOUS REACTION!!!!! Throat closing is serious!!!
To start a food challenge you eat a teaspoonful or a single small bite of a possible food. Of course you write the time and what and how much you are eating. Then, 20 minutes later, if there is no reaction, you double the dose (2 teaspoonsful) and write that down also. 20 minutes later you double that dose, wait 20 minutes and finally double that dose. If nothing happens you can feel that you don't likely have a problem with that food.
You can do this test in the allergist's office for foods and drinks that might give you a slightly serious problem, but they won't let you test something you are sure is dangerous. Don't do anything dangerous at home!!!!!
You have listed several possible food triggers. What about what you drank at the same time? Did you take any medicines those days? This can be tricky.
When you get a list of allergies, or even one food or drink that you are sure gives you a serious reaction you can google it with the term food allergies or food intolerances and find out a lot more information.
Since the ranch dressing is made of several ingredients you may have to break that down into components for further testing. Just milk, or whatever else is in it.
Since your reaction seems like a possibly serious allergy, you might wait until the skin tests for most of the ingredients - much safer!