The most common form of eczema is atopic eczema, which can affect any part of the body but is often found inside the elbows, knees, on the neck, hands, cheeks, and scalp. The cause of atopic eczema is unknown, but it often runs alongside other conditions including asthma and hay fever, and flare-ups are triggered by things such as soap, laundry detergent, stress, the weather, and occasionally food allergies.