Eczema is a skin condition that makes skin become itchy, red, or dry, due to inflammation.1 Atopic dermatitis is its most common form.
In general, eczema is a chronic, and most likely, genetic condition.
When the skin becomes inflamed or irritated, it could lead to small patches of skin turning whiter or lighter because of pigmentation, compared to the other nearby areas of skin. This contrast in discoloration may be more apparent on those with darker skin. To get more technical, this is what happens when an eczema flare-up resolves itself "through the sub-acute phase and settles back to dry skin without inflammation".
If you’re seeing white patches on your (or your child’s) skin as a result of eczema, don’t worry: over time they do tend to fade.