There are a few different types of body reactions that end up clustered under the word 'allergy'.
An IgE allergy (the true, scientific definition of the word, and ones we tend to focus on here) cause runny nose, congestion, shortness of breath, hives, anaphylaxis, etc. and possible death. aka a histamine response.
An IgG allergy is an intolerance. Just as real and annoying and a major pain to deal wtih, but not deadly if you get slipped a bit. They tend to cause mainly gastrointestinal issues but can cause emotional and behavioral issues too. They won't send you into anaphylaxis, which is why the distinction between scientific allergy and intolerance is important.
Both IgE and IgG can be tested through blood. You mentioned a skin test - did that come back positive too?
From what you've mentioned, it sounds a whole lot like celiac to me. An IgG test would come back positive for gluten if you have celiac, it's one of 4-5 blood tests for it. Celiac causes digestive issues, and when I was concerned I had it, I ran across many people online who 'went off the deep end' so to speak when they got 'glutened'. Do you know if your doc tested you for celiac? It's important to know, because it raises your risk of bowel cancer in the future.