Hi, I’m Dr. Peter Lio and I’m here to answer some of your questions about eczema. Today’s question is: “What causes eczema?” This is a great question and unfortunately we don’t have a great answer. But some of the pieces that are important in thinking about how eczema happens include the fact that the skin barrier is leaky. So we know that the goal of the skin is to keep water in, and to keep things like bacteria and viruses, allergens and irritants out. So when the skin is strong it’s doing its job, but if the skin becomes leakier and that barrier is damaged then we lose water and those unwanted things enter in. This in turn triggers an inflammation response. The immune system is normally there to protect us, but in this context it begins to go crazy, attacking the skin, causing more breakdown, which fuels the process and also causing itch which is another important component of eczema. That itch creates a cycle of scratching which again further damages the barrier, which further allows more stuff to get in and causes more itch, so we become stuck in this vicious cycle. All of these things work together to cause trouble. And we also know there’s a role for bacteria as well. When that skin barrier is damaged, abnormal colonization by bacteria – particularly staphylococcus – further worsens this. In sum, we know that there are multiple factors playing a role. We don’t fully understand which is the most important for each patient, and that’s part of what we’re trying to understand. Although we know that no matter where you begin all of these things can play together to cause the disease. Thank you very much for watching and we’ll see you at the next one!