Poison ivy (also poison oak) contain on their leaves the chemical urushiol, and with skin contact the oily chemical adheres to skin, where it can pass through intact skin and is metabolized. The immune cells primarily involved to create the skin reaction are T-cells. Every year when I garden in the spring I seem to get poison ivy, even though I am careful, it also seems worse every year. It starts as a few painful serum-containing blisters on one or two digits, that are painful, burning and associated with redness, and I hope that will be it. No pustules. Then it progresses to involve much of both hands and now this year part of my face and torso, over a course of 4 days, and then generally resolves by about 2 weeks. I don't think all the areas affected I had exposed to poison ivy, but I suspect T-cells from prior contacts remain in location in the dermis/superficial subcutaneous tissue and get re-ignited when other cells that have been in contact get excited. There is no pustulation. Skin findings somewhat resemble GDD.
There are a lot of similarities with GDD in that both do not result in pus-formation, hence the early immune system military force of neutrophils (which create pus) do not play any significant role. Bacteria are primary antigens that excite neutrophils. Delayed findings are critical in both conditions. This reflects T-cell activation, and as with poison ivy, I have opined that T-cells play a prominent role with GDD.
The prominent similarity is that the host response is the entirety of the condition. With poison ivy it may be just T-cells. GDD likely involves a number of immune cell lines, as I have described before. Early skin flushing and related changes with GDD, likely represent primarily mast cells. T-cells and possibly others, such as macrophages, represent the intermediate symptoms (1 week to several month onset, which are most of the symptoms) then delayed findings, especially fibrosis (if it occurs) is a reflection of bone marrow cell infiltrates, the circulating fibrocyte the best known of these. This is the principal cell line in NSF, an uncommon cell line with GDD (thankfully).
One would think that everyone reacts to urushiol, since skin reaction is so common, but about 10% of individuals do not react. This is the inverse with GDD in that no more than 0.1% of individuals who get injected by a GBCA have significant GDD type symptoms.
Poison ivy remains restricted to the skin, it seems in everyone - this may be thanks to T-cells and maybe the primary skin immune cells, the Langerhans cells, that block deep extension. I suspect there are some cases of oral consumption. I am not serious with this, but it would be interesting if urushiol was injected intravenously, where it would deposit to, and how closely it would then simulate the entire picture of GDD.
T-cell involvement in antigen exposure diseases: poison ivy and GDD.
Richard Semelka, MD.