I have a number of patients suffering from eczema, and came across this handy list in Acupuncture Today of the possible triggers. In Chinese Medicine, eczema can present with many different patterns and one treats accordingly.
milk
eggs
peanuts
soybeans
fish
wheat
dust mite allergies
pollen allergies
over-washing hands
frequent bathing
pregnancy
menstruation
thyroid imbalances
infections (staph, strep, or herpes simplexa0
Dry, cold weather (decreased humidity)
sweating
wool clothing or blankets
emotional stress (a trigger, not a cause)

Info on my practice here.