There are dozens of types of eczema and as I mentioned I have 3, Grover's is just one type. You may also have multiple forms. This confuses doctors as they often keep treating symptoms as they should for your originally diagnosed form. My ACD was absolutely the most miserable form I had (I still have as it is for life but am symptom free) and it was the first type I developed. My first symptom was hand eczema. Mainly because I turned out to be allergic to my dish soap (preservatives), protective gloves which had an element of rubber in them, MBT also I garden and used hoses with rubber and held them without protection. Now I use vinyl hoses or wear vinyl gloves if touching a rubber hose. I was also allergic to all my topical moisturizers, except plain old Vaseline. Even my linens if not 100% cotton. I am even allergic to 3 of the 5 classes of steroids. With each allergic contact your reaction time is less and the symptoms more severe. This test saved my life!!! I was ready to end it all because the 24/7 pain and itching escalated and became unbearable. Sleep was impossible. It progressed to where I became allergic to more and more elements, yes some of the allergic elements are natural. Yes rashes can spring up everywhere or you may have no rash symptoms to show but it internalizes and for me it felt like my nerves inside my skin were inflamed. I would get taser like stinging and burning randomly anywhere. Itching and stinging always worse at night as our histamines are elevated in the evening. ACD is probably the second most common form, after Atopic.
Like you I never had a skin allergy till middle age. Not even acne. For me it was around my menopause time at age 50. It's most common to get ACD later in life as our body looses it's ability to tolerate what it believes to be a poison. Your body is raising your histamine warriors trying to kill off what it considers poison, a common ACD allergy for those in the medical profession is latex. Working with many latex products for decades the nurses and doctors have been absorbing the latex though their skin. It goes into the blood stream and finally the body says "no more", raising histamines to try to purge it. Thus rashes, inflammation and itching. Your rash doesn't even have to be at the contact site because the element that is off gassing and transferring through your skin and has entered your bloodstream can manifest a histamine reaction anywhere. Perhaps this is why you develop rashes in random places. A common area of sensitivity is the inner elbow. Most derms recommend trying a new topical in the inner elbow for 2 weeks before putting else where on your body. Often this site will react the soonest to allergies.
Even if you test negative to anything, the test will give you direction. You will know to keep searching for the correct type of eczema If you are allergic and have ACD you can eliminate contacts and be ACD free like me because now you will have names of your tormentors.
Have you gone to the New Zealand Dermatology site and searched all the forms of eczema? You can view photos of each type and perhaps you will see a rash that looks like yours and that can help identify your type.