Seems like you know for sure you have 2 forms of eczema and Contact Dermatitis, CD, is closely related to Allergic Contact Dermatitis, ACD, the symptoms are just are delayed. Also with ACD it travels thought the body. You could be sleeping on a memory foam pillow for example and memory foam is made with an element from rubber, unlike polyurethane foam which isn't, the memory foam off gasses though your skin and you could react internally throughout your body if you have a rubber or rubber element allergy. I know this happened to me. My new memory foam mattress turned out to be killing me. It sounds like your doctor ordered many tests, but I am still confused. Did you Google the 5 Day Extended Patch Test? What was the name of your test kit? How many test sites? Perhaps some kits test in fewer days than the TrueTest. Normally application is day one, then day 3 1st reading and day 5 2nd reading and removal. Many allergens don't show up until day 5 and for some folks it's left on even longer. The patch kit test for chemicals and natural elements like rubber, preservatives, adhesives, fragrance, and so on it doesn't test for scallops or dust mites. The environmental tests, test for dust mites, pollen, grasses, mold, pets and such and that is a simple 30 minutes skin prick test done in the allergist or dermatologists office while you wait. If you are not sure if you had an extensive patch test kit, like the True Test, call your doctors office and ask for copies of you test, even if results are negative. My original testing was for about 78 sites, but recently had a metals panel done, another patch system of the True Test which wasn't run before. I keep records of all my test results positive or negative.
From what I know your doctor is right thinking the scallop or dust mite allergy isn't effecting your skin. I also have environmental allergies, have had these since childhood and antihistamines help with my symptom which is hay fever.
When our histamine level is elevated in our bodies it's easy to test. My derm told my husband to watch as he took a retracted ball point pen and very lightly wrote my name on my back. I had a red welt with my name showing.There is actually a medical name for this happening. Sounds like it is happening to you. I am wondering if elevated histamines are the cause of your reaction to getting bumped (your bodies histamines are fighting to rid you of something upsetting them and they are over producing).
As I mentioned there are many types of eczema and so diagnosis is not that simple as some of us have multiple forms with overlapping symptoms.
The New Zealand Dermatology site is the most extensive I have found in my searches, it actually lists GD which even the NEA site doesn't. Go to this site and study all the photos of any type of eczema that seems related to your symptoms. Study the photos, very graphic and many rashes will be far more severe than you have, but keep looking. That is how I figured out I had Perioral Eczema. I was helped by a blogger who shared about Perioral (I had never heard of it). Originally derm told me I had Rosacea or perhaps ACD issues (I had eliminated all my allergic contacts). Anyway after searching pages of photos of Perioral, bingo I found a rash just like mine, same location and appearance. I copied all info and took into her and she looked at it and said "Oh yeah that's what you have". Still I forgave her treating it incorrectly as she is the only dermatologist that told me my torso rash was GD, others had been treating it assuming it was ACD.
Right now, if not using already, order Grandma's Bar soap for Face and Body, previously known as Grandma's Lye Soap. Only 2 ingredients: lard and lye. Lye is transformed into glycerin in the old fashioned soap making process so all you contact is lard (moisturizing) and glycerin (moisturizing). I don't know anyone allergic to it. I keep a bar at each sink and shower and when at my worst wash my hair with it (works best for hair with soft water). Once I got my scalp calmed down I searched with my CAMP list from my True Test kit and found a safe shampoo for me. Safe doesn't mean it will work for me, as 1/2 of the items recommended should work but don't. So there are more allergens I am unaware of that I haven't been tested for. Yet the VMV Clark Wash is safe for me.