Immunotherapy was originally done by injection. In the sublingual version, which is apparently used in some European countries, Italy in particular, a doctor (or "wellness practitioner," I suppose) puts a droplet of solubilized allergen under your tongue. You process the allergen and the idea is that your immune system, after a controlled overdosing, becomes tolerant of it--in the same way that our immune systems are generally tolerant of self-antigens.
Our bodies have the ability to become tolerant of allergens, it would appear. I am not familiar with the mechanism (time to dig out my copy of Kuby) but evidently I'm in the company of the medical profession; otherwise this type of therapy would be more successful and, you'd think, approved by the FDA.
SLIT, as those in the know call it, isn't approved by the FDA. That doesn't mean it doesn't work in some cases, or couldn't work in more cases if the dosage, formulation, etc., were optimized. (It does seem to me that SLIT would only work for you if your eczema is primarily due to one allergen.) Many FDA-approved treatments don't work or have nasty side effects. And sublingual immunotherapy, although perhaps less effective than the kind that involves a needle, does no harm to most patients (see: Hippocratic oath). Mind you, don't be the one who goes into anaphylactic shock.
So, I say, go for it, if you have the money to spare-- your insurance won't cover it in the U.S.-- and good luck. That is my attitude to eczema therapy and I've applied it to myself over the years. For example, my dad, a globe-trotting geologist, came back from Morocco with a small bottle of black cumin oil. He'd been in some street bazaar and had told a fez-wearing purveyor of unguents (see: wellness practitioner) that his son, who lived in the U.S., had always suffered from eczema. The merchant advised him that he had a guaranteed cure: "huile de nigelle," or black cumin oil. I think it's this stuff.
Read that Wikipedia entry. There's a quote from the Prophet Mohammad.
"Aisha has narrated to me that she heard the Prophet saying, 'This black seed is healing for all diseases except As-Sam.' 'Aisha said, 'What is As-Sam?' He said, 'Death.'"It sure sounds like black cumin ought to work for eczema. (For "death" see: disease to end all diseases.)
For one week, I rubbed black cumin oil on my eczematous patches on one side, and left the other side untreated. No effect, unfortunately. It could be that it doesn't work on atheists.