This is general information about celiac disease and dermatology. For individual diagnosis one must see a physician. A primary care physician is a good option, as they can diagnose celiac disease, it is usually not necessary to see an immunologist or dermatologist.
Dermatitis Herpetiformis does have a differential diagnosis.
First, consider other conditions that could mimick DH like bullous pemphigoid, herpes, uritcaria, eczema, etc.
- DH is often confirmed by a biopsy and testing for associated conditions that are suggested by other symptoms.
Even for confirmed DH, however, consider that celiac is not the only disease associated with DH.
- UpToDate states that the next most common associated condition is autoimmune thyroid disease, and others include type 1 diabetes, pernicious anemia, vitiligo, Addison's disease, alopecia areata, some other autoimmune diseases, and non-Hodgkin lymphoma.
Remember that correlation does not imply causation - this means that just because they occur together does not mean one causes the other, or that they are certainly caused by the same thing. It just means that there's an increased likelihood of having one of the other conditions.
However, the added time-consistent direct correlation of gluten and the rash would very strongly suggest celiac and make other associations unlikely.
So, is it diagnostic of celiac disease then? Can you definitively rule in or out celiac?
Diagnosing celiac disease incorporates multiple aspects including clinical history, exam, and usually lab testing.
Consider that gluten does not exist in isolation; it is a component along with many other components in certain foods. It is possible, though less likely, to have a skin reaction to a different component in the same food.
This article in a GI Journal states the current recommendation:
...interpretation of serological testing requires consideration of the full clinical scenario.
I have seen some providers consider one feature of celiac disease as clinically diagnostic, and therefore treated as such without necessarily confirming with blood tests: the repeatable correlation of resolution of gastrointestinal symptoms on removal of gluten, and recurrence of symptoms upon reintroduction of gluten.
However, there are other associated recommendations are to do the blood testing to have a more concrete diagnosis. UpToDate recommends:
As a general rule, testing should begin with serologic evaluation. Immunoglobulin A (IgA) anti-tissue transglutaminase (TTG) antibody is the single preferred test for detection of celiac disease in individuals over the age of two years.