It is a common misconception that eczema is caused by food allergies. Indeed, food allergies are far more common in eczema patients than in patients with a normal skin, but are usually not the “cause” of eczema. Up to 40% of patients with moderate to severe eczema have a food allergy of sorts, most commonly to egg, peanut and cow’s milk. This is more common in children with early onset eczema less than 6 months of age, and in those with severe, treatment-resistant eczema. In less than 20% of cases does the ingestion of these foods lead to the eczema. More commonly, these foods cause a typical immediate reaction in eczema patients, such as hives and rashes, and maybe even more severe reactions such as breathing difficulties. In the minority of eczema patients such foods actually cause eczema flares.
Certainly, blanket elimination diets are not to be used in eczema patients. Therefore, if the patient or clinician is concerned about food allergy in eczema, rather have a proper assessment by an allergist, who can determine exactly which foods may be involved.
Interestingly, although many people believe that food allergies cause eczema, which we have now learned occurs in the minority of patients, it is true that the opposite relationship is more common: eczema can cause other allergies such as food allergies and also respiratory allergies. This is because a broken skin barrier can let allergens through the skin and set up an immune response which can lead to allergies.