I’m afraid I don’t keep track of citations electronically; I will add in citations after the last post. There will be at least 4 parts.
So when I say 25-60% of eczema cases result from detergents, I’m really considering the commonality of circumstances under which detergents would likely be the overwhelming factor in the outbreaks. These circumstances vary.
Because adults often have more complicated health pictures, and because they have naturally less permeable membranes, I would expect detergent as the overwhelming influence in a smaller percentage of cases than for infants or children. For infants, with their far more permeable skin and their still-training immune systems, the percentage is far higher.
Although, as I said, sometimes people can resolve the outbreaks by addressing one modulator or another, or all of them at once if relevant — the primary ones being detergents, environmental (or internal) mold/fungal/yeasts (or, for the internal, let us say, significantly imbalanced microbiome and consequences), or (typically certain protein) foods, or even in some cases the state of the immune system or membranes (skin, lung, and/or gut) health, because it’s all related — I think generally it’s possible to estimate how often the different major modulators dominate.
As you know, a number of studies have shown that pregnant women given beneficial bacteria (probiotics) during pregnancy reduced the rate of eczema in their infants by roughly 20%.  It is my belief that these cases are the ones in which an imbalanced microbiome /fungal modulator would dominate had the eczema developed. Probiotics do more than just compete with fungal organisms, Lactibacillus has also been shown to repair the gut barrier.  (Also an important tangent I won’t go into, but this relates to the role of bio-surfactants and how environmental syndets interact.) Not that removing external detergents wouldn’t help those who would have developed eczema absent the probiotics— and there is overlap in the environmental strategies, relating to gut/membrane health as well — but for this segment of infants, about 20-30%, I feel the evidence suggests the fungal modulator dominates.
My observation from experience is that those for whom food is the overwhelmingly dominant factor is about 10% of cases. This is not a hard and fast number, it’s just based on experience, and could change based on conditions. As you know, even the rates of eczema around the world continue to change rapidly.
Other studies tangentially suggest roughly the same proportions: “…two-thirds of patients with atopic dermatitis have no measurable allergen-specific IgE. Are we not just measuring the right IgE? Perhaps, but not likely, considering patients with X-linked agammoglobulinemia (a disease in which patients have almost no IgE) commonly develop atopic dermatitis.”  (Note: IVIG, at least at the time of this paper, is normally processed with detergents and patients with X-linked agammaglobulinemia, I believe, need regular infusions. Again, not to go into a long discussion, but write back if you don’t see the applicability here.)
Noted Harvard pediatrician Dr. T. Berry Brazelton, whose writings in his book Touchpoints  gave me the spark that led to my own solution, observed in his book that he could prevent most cases of childhood eczema by identifying atopic parents and having them implement general allergy-healthy-home practices and avoid using detergents with their infants. I asked him just as you have asked me, on what research he based his recommendations, but he said it was just based on decades of medical practice and observation.
In his day, of course, there were fewer sources of syndets in home environments, and they tended to be less powerful. Given the instructions he gave, he would have been addressing the two most significant modulators. Given that this eliminated most cases of eczema — and considering the environmental differences between then and now — I feel his experience further corroborates my observation that the cases in which a food (usually a protein food from a short list) is the primary modulator and removing it completely resolves full-body eczema as well as fluctuations from various triggers, represents the smallest percentage of cases from these main modulators. (Let me repeat that none of these factors occurs in isolation, the food modulation relates to the state of the gut barrier, which can also relate to detergent ingestion and unhealthy balance of microflora.)
Although my perspective and problem-solving heuristic are novel, there are researchers who have been publishing along similar lines and whose work supports these contentions. The most notable is probably respected dermatologist Dr. Michael Cork in the UK, who has for many years had success when his patients remove all surfactants entirely. He does not make the distinction between soaps and detergents as I do — he writes about not using “soap” because of presumed consequences to the skin, but then goes on to underscore it by saying many “soaps” have detergents in them anyway.  I wasn’t aware of his work while we were problem-solving, but I think he has been publishing along the lines of surfactants playing a role in the eczema epidemic for years prior.
So our views are very similar. The main difference and a significant limitation of the no-surfactant approach is that it’s not really very acceptable to most people to refrain from getting clean — Dr. Cork’s assistant said this to me, the trouble is getting people to do it — and in my experience as well as my understanding of the problem, it’s not really necessary to refrain from washing. In fact, many of my site users (including doctors using the site) have commented on how healthy their skin remains even when they engage in frequent hand washing.
The main difference stems from perspectives on how skin is affected by washing. From empirical observation, I have come to see dryness and other impacts from washing as resulting from the residues of highly hydrophilic compounds ON the skin, because of the molecular properties of those residues and how ubiquitous those exposures are in modern environments, rather than the stripping of lipids from the skin by washing, which is the traditional view.
In fact, avoiding the use of traditional soaps with molecular properties that do not cause the kind of increased permeability that most modern syndets do, actually makes it more difficult to get results in typical modern environments. Where most people with uncomplicated histories can see results in as little as a few days to a week with my site strategies, and those with more complicated histories on the order of a few weeks to a few months, these no-surfactant-at-all approaches seem to take on the order of 6 months to 2 years, and the outcomes seem less satisfactory.
In relation to the abnormal influence of modern syndets, in my observation, everyone experiences a change in circumstances because of this environmental influence — degraded skin quality, often dryness that most people believe is inherent, otherwise increased susceptibility to allergic symptoms or amplified symptoms where an allergy already exists, exacerbated asthma — even though not everyone experiences eczema. Anyone under the age of 5 and over the age of 50 especially benefits from minimizing this influence just in skin quality. I believe virtually anyone has the capacity to express eczema under the right conditions, though. Certainly, worldwide eczema and atopy rates continue to rise, seemingly without bound. And in Sweden, which has some of the highest rates, researchers have noted the environmental factor seems related to something in the indoor environment. 
In any given situation, removing detergents, or changing another threshold factor (mainly environmental mold or certain protein foods, including via gut barrier health), or both, might bring a given person’s circumstances below the threshold of any potential for triggering the reaction. If a person’s outbreaks could have resulted because of more than one factor, but that person removed only one of them and stopped reacting because of bringing a threshold up, that person would blame the eczema on that one thing, when they might as easily have achieved the same result, at least in the short-term, by removing the other factor.
I have had the experience with the site that some people will work very hard in their daily lives to remove triggers that cause outbreaks with each exposure — a pet, for example — only to find that when they follow the site strategies and go detergent-free, they can bring the pet back without the same breakouts or other allergic symptoms. (This is simpler with a dog; many cat litters have significant amounts of detergent in them or are otherwise highly hydrophilic compounds, but with the right awareness and choices, that influence too can be avoided.)
To be Continued in Part 4:
“To the question of estimating what percentage of the eczema/atopy problem relates to detergents … implies a broad understanding of the problem across the population …”
 Pelucchi, Claudio, Liliane Chatenoud, Federica Turati, Carlotta Galeone, Lorenzo Moja, Jean-François Bach, and Carlo La Vecchia. “Probiotics Supplementation During Pregnancy or Infancy for the Prevention of Atopic Dermatitis.” Epidemiology 23.3 (2012): 402-14.
 Rao, R. K., and G. Samak. “Protection and Restitution of Gut Barrier by Probiotics: Nutritional and Clinical Implications.” Current nutrition and food science 9.2 (2013): 99–107. Print.
 Anderson, P. Chris, and James G. Dinulos. “Atopic Dermatitis and Alternative Management Strategies.” Current Opinion in Pediatrics 21.1 (2009): 131-38. Web.
 Brazelton, T. Berry, and Joshua D. Sparrow. Touchpoints: Birth to 3. Cambridge, MA: Da Capo, 2006. Print.
 still ISO this paper, I have the print somewhere… It’s an older paper than I am finding easily on Pubmed
 Aberg, N., B. Hesselmar, B. Aberg, and B. Eriksson. “Increase of Asthma, Allergic Rhinitis and Eczema in Swedish Schoolchildren between 1979 and 1991.” Clinical Experimental Allergy 25.9 (1995): 815-19. Print.
This work by A.J. Lumsdaine is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License