Recently, I had a conversation with my friend and colleague, Dr. Eddie Valenzuela about the relationship of food and eczema. A link to our discussion is here. I receive questions about eczema all the time but one stands out, "Can I do food testing to evaluate eczema?" Like a lot of things in the field of Allergy/Immunology, the answer is: it's complicated.
First off, we'll start with the basics. Eczema is a complex disease. It's characterized by dry, itchy skin and is sometimes called "the itch that rashes." The origin of every patient's eczema is unknown. Theories include problems with the skin barrier, immune regulation problems, or changes in the bacteria that live on the skin. 11-15% of American children have eczema and adults can be affected too. As of now, there isn't a cure for eczema.
The current standard of care for eczema centers on the following three things: 1. intense moisturization 2. controlling itch 3. identifying and avoiding triggers. Due to the complex nature and triggers of eczema, controlling one particular thing will not guarantee control of a patient's eczema. Potential triggers can include (but are not limited to) stress, anxiety, lack of sleep, humidity, dryness, heat, cold, environmental irritants, or food triggers.
Now that we've established that eczema is a complicated issue with a multitude of triggers, let's talk a little about food allergies as well. If someone has reactions to foods, it could potentially manifest in different ways. A true food allergy will show up quickly, usually within minutes to hours, with some combination of hives, throat closing, wheezing, vomiting, diarrhea, or low blood pressure. It is caused by a very particular pathway that is triggered by a pesky antibody called IgE. If your body produces a specific IgE to something that it subsequently encounters, you could experience the allergy symptoms that I just mentioned. Allergy testing is looking at that particular pathway which is mediated by IgE.
Food-triggered eczema seems to be part of the non-IgE mediated pathway. The reactions are delayed, sometimes by another day. Non-IgE mediated processes will generally not benefit from specific IgE (blood) or skin testing. Misinterpretation of these tests can lead to elimination of foods unnecessarily if there isn't a clinical history that backs the result. Ironically, eliminating a food that somoene eats consistently could actually lead to an actual allergic reaction when it is reintroduced back into the diet.
With this being said, you're probably asking, "So how am I supposed to identify what particular food may be triggering the eczema??" I'm sorry to say there aren't any easy answers. A food diary is always a good place to start. Writing down all the foods that you've eaten and then trying to evaluate for patterns in timing of symptoms is a good place to start. Before eliminating any foods, it's important to speak with your doctor to form a plan. There have certainly been patients, especially infants with severe eczema, who have benefited from targeted elimination diets but doing so under the supervision of a doctor is best.
While eczema can sometimes feel maddening, there is hope. Most patients can be controlled with aggressive moisurization, various topical medications, and itch control. 40-70% of children will outgrow their eczema by the time they're 4-7 years of age. In addition, more and more treatments are becoming available that have shown great promise for controlling eczema. Let us know if we can help in your journey to control of your eczema.