I thought I would post the lab report verbatim, for any of you in the veterinary field, to see if any of this rings a bell for you:
Slide 1: Haired Skin (Metatarsals and Metacarpals): Follicles vary from miniaturized to being in anagen. Low numbers of lymphocytes, plasma cells and macrophages dissect through the superficial dermis and form sparsely cellular perifollicular and pervascular aggregates. A few epithelioid macrophages surround a single adnexal unit. A small amount of finely beaded basophilic material (mucin) expands the superficial dermis. A small focal ulcer has low numbers of underlying neutrophils admixed with small amounts of fibrin. The epidermis is mildly to moderately hyperplastic, with occasional rate peg formation and scattered lymphocytic exocytosis.
Mild chronic diffuse lymphoplasmacytic dermatitis
This lesion is nonspecific. Alopecia and follicular miniaturization may be associated with excess endogenous or exogenous estrogen exposure (huh??), although conditions resulting in systemic hyperestrogenism result in lesions which typically spare the distal limbs. Alopecia X may be associated with adrenal sex hormone imbalance or abnormalities in hormone receptors at the level of the hair follicle. This progressive condition also typically spares the distal limbs.
As two unrelated animals in the same household are affected with similar clinical signs and distribution, it is likely that exposure to an exogenous chemical or hormone is resulting in stimulation of distal limb follicular hormone receptors.
There is no evidence of neoplasia or infectious agent in the specimens examined.
How frustrating!! Clearly its not alopecia since like they said, you have 2 unrelated dogs. But I'm sure you already knew that. The type of dermatitis they saw would be typical with an allergic reaction or a localized irritant.
Depending on where in the country you live, if this is something in your yard, you might not have a flair again until the spring if everything freezes. So that may be good to help you eliminate the exposure there. I'm sure you're driving yourself crazy trying to figure out what they are reacting to. Its such a crapshoot!
my guess would be some kind of insect growth regulator, something that is sprayed around the home, yard, neighborhood.