my dd3 has mild exema and i notice that it flares up in hot water when she has a bath or shower. Maybe thats why its worse for you in winter. Do you have hotter showers when its cold?

Also, i was told by a fiji lady that coconut oil is used by them for all sorts of skin ailments. It has some really good healing properties in it which keep the skin in good condition...much like olive oils.
If you want to try something natural without chemicals, then go for olive or coconut oils that you buy from the supermarket in the cooking oil section.