@Matt13  I understand where you're coming from.  Seemed I was reacting to all sorts of foods there for a while, but a low histamine Paleo diet really helps.   We make histamine in our bodies as a useful  neurotransmitter (causing alertness), and also as a response in the immune system.  Histamine is made and released by Mast Cells.  Mast Cells can become hypersensitive to stimulus and release histamine easily, like having an itchy trigger finger.  Mast Cells need Thiamine Vitamin B 1 Benfotiamine in order to NOT release histamine.  Mast Cells that do not have sufficient Thiamine release histamine easily and at the slightest provocation.   Plants and other animals make histamine, too.  By removing high histamine foods from the diet, more histamine can be removed from the body.  We need Pyridoxine, Vitamin B 6, Vitamin C, Cobalamine, B12, and Thiamine B1 to make Diamine Oxidase, an enzyme that breaks down histamine.  If we don't make sufficient DAO ourselves, DAO supplements are available over-the-counter.   Removing Nightshades (tomatoes, potatoes, eggplant and peppers) was very helpful.  Nightshades contain alkaloids that cause Leaky Gut Syndrome wherein large molecules of food can pass through the walls of the intestines into the bloodstream, traveling to other organs and structures where they promote inflammation.   After a few days on the low histamine Paleo diet, the Autoimmune Protocol diet, I started feeling better.  My diet was really restricted, but I felt so much better, I stuck with it.  Eating foods that were easy to digest and low in histamine allowed time for healing.  After a few weeks, I was ready to add one food at a time (two week period) back into my diet.  I had setbacks when I ran into a food my body didn't like, and had to go back to the start, but it was worth doing.  Celiac is a marathon, not a sprint.   Blood tests are not accurate measurements for various B vitamin deficiencies.  Vitamin levels in the bloodstream are different from the amount stored inside cells inside organs where they are utilized.  You can have symptoms of a deficiency yet have "normal" blood levels.  The best way to test for a B vitamin deficiency is to take it and look for health improvement.  B vitamins are easily excreted because they are water soluble.  Malabsorption in Celiac can affect all the vitamins and minerals our bodies need, not just one.  Do talk to your doctor and nutritionist about supplementing while healing.  

A little late to the party in terms of seeing this and responding to it, so apologies! But I wanted to responds as this sounds exactly like my experience. I had covid, followed by shingles, followed by strep… that unlucky bout of infections is what lead me here with dermatitis herpetiformis. I was also self diagnosed in the beginning and turns out I was absolutely right! Currently waiting for biopsy confirmation though. In terms of swollen lymph nodes, I get this when my rash is present. Mostly in my neck and they’re a lot more swollen if I’ve been cross-contaminated with gluten and when the rash is at its worst!   

Welcome, @Morgan Tiernan, The best thing to clear my dermatitis herpetiformis is to take Niacin, Vitamin B 3, the form called nicotine acid, the kind that causes flushing of the skin.  Flushing Niacin clears my skin quickly.   Yes, the flushing might seem really strange, but it opens the tiny capillaries in the surface of the skin which helps remove the antibodies that gather in those pustules.  The flushing lessens the longer Niacin is taken, but still works at keeping the blisters away.   Be sure to take a B Complex and Benfotiamine, a form of Thiamin , Vitamin B 1.  Covid, shingles and other infections like strep throat deplete our Thiamine quickly.  Having frequent infections can indicate low Thiamine.  We have a higher metabolic demand during infections, physical trauma or surgery, emotional and mental stress, and while physically active like dancing.    Thiamine has anti-virus and antibacterial properties.  The eight essential B vitamins work together.  Taking Benfotiamine in addition to the B Complex is safe and nontoxic.  Excess B vitamins are easily excreted because they are water soluble.  New Celiacs are often low in vitamins and minerals due to malabsorption.  Vitamin D can help calm the immune system.  Following a low histamine Paleo diet , like the Autoimmune Protocol Diet by Dr. Sara Ballantyne, a Celiac herself, is also very helpful.  Steroids lower histamine, but the low histamine AIP diet is safer.   This research may be old, but Flushing Niacin does work!!! Nicotinic acid therapy of dermatitis herpetiformis https://pubmed.ncbi.nlm.nih.gov/15412276/ P.S. Wearing natural fibers helps my dermatitis herpetiformis.  Synthetic fibers keep sweat next to the skin, causing further irritation.  Natural fibers wick moisture away, keeping skin dry and exfoliated.

Hey @Rogol72! thanks for your very helpful response. Those videos are great and super educating! I’ve forwarded them to my family members too as often it can be very difficult to explain to those around you just what you’re going through. Though, I’m fortunate that they’re super supportive and keen to help me get to the bottom of the problem. Interesting how you mentioned soaps and shower gels irritating too! Is it better to rinse off the sweat straight after exercising just with some cool water? Additionally, is minimising soap in those areas during showering helpful too? Or is there a particular soap that may be helpful! I have some more questions about dapsone too, if you don’t mind me asking. As mentioned in my response to Trents, I take prednisolone for when I am glutened or when my symptoms become too unbearable. With oral steroids it’s usually a 4 week dose as I have to reduce my dose to slowly come off them. How long can you take dapsone for? Can it impact your immune system in the same way as oral steroids (I have to be super careful I don’t pick up any infections whilst on my steroids as my immune system is compromised.) Yes, I’m from South Wales in the UK. Though my grandfather is Irish, explaining my surname (very well spotted!)