Winter months are very difficult for people with some forms of eczema (called atopic dermatitis by doctors), while others will have more problems managing their symptoms during the summer. The reason for the first likely has something to do with the decreased humidity that is prevalent in the winter, and those with summer time exacerbations are likely made worse because of the heat. Obviously, moisturizing is with thick creams and lotions is the first line therapy, but if your symptoms do not seem to be controlled appropriately with these alone, then there are many other options available.
Our understanding of eczema is evolving with time. Whereas before it was thought to have something to do with an allergic reaction, we now believe that it is more due to the inability of the skin to function properly as a barrier. This both allows extra allergens into the deeper tissues of our body, as well as allows the moisture that is normally retained in your body to escape. If you are having symptoms and trouble controlling them despite your best efforts, you should speak to your primary care doctor
to see what treatments might be the best for you and your seasonally worse eczema.