Though the specific cause of eczema is not known, underlying genetic factors are known to play a part. Experts believe it may be caused by a dysfunctional skin barrier and an overactive immune system that responds aggressively when exposed to irritants. Eczema may be triggered by: Food Sweat Stress Insect bites Temperature changes , especially heat Chemicals in soaps, fragrances and detergents Synthetic or rough scratchy fabrics , such as wool Skin issues , such as a high bacterial skin load or inadequate moisturising Environmental allergies such as pollen, dust or pet dander Infections , such as upper respiratory tract infections