Your bundle of joy at 3 months old suddenly starts developing red crusty cheeks. Your 1 year old has itchy, crusty, red folds of the elbows and behind the knees. What gives?\u00a0 These are symptoms of eczema also called atopic dermatitis. This flaky, itchy, scaly, irritated condition occurs in different characteristic locations at different ages. As children start to get over the age of two the rash that was on the face and in the folds of the arms and legs will usually start to migrate to the outside of the elbows and knees.\u00a0 Now that we have defined what eczema is we should look at what causes eczema in babies. Role of Family History on Eczema in Babies About 70% of children with eczema have a family history of eczema or asthma or allergic conditions. Sometimes clinicians lump these 3 conditions together and call this atopic disease or atopy.\u00a0 If you have one parent with eczema, asthma or allergies there is a 2 to 3 fold higher chance that a child will develop eczema.\u00a0 If you are reading this and both you and your spouse have eczema, asthma or allergies there is a 3 to 5 fold chance that your child will develop atopic dermatitis. Does reducing egg or cow milk from a breastfeeding mother's diet improve eczema? The American Academy of Pediatrics (AAP) released a new report in 2019 addressing what we know on what causes eczema in infants. \u201cCurrent evidence does not support a role for maternal dietary restrictions during pregnancy or lactation\u201d. In fact, trying to restrict foods like eggs or milk may lead to a baby with a lower fetal weight gain in pregnancy. What is the role of exclusive breastfeeding and fancy formulas on eczema and atopic disease? The clinical report by the AAP goes on to talk about the benefits of exclusive breastfeeding for 3 to 4 months, saying it decreases the incidence of eczema in the first 2 years of life. However, there are no short- or long-term advantages for exclusive breastfeeding beyond 3 to 4 months for prevention of atopic disease. There was a time that we thought giving extensively hydrolyzed formulas could prevent eczema, but it looks like there is now a lack of evidence to make this claim. Extensively hydrolyzed formulas are used in kids who have milk protein allergy and can run double the price of regular formula. So when considering what causes eczema in babies we can now utilize regular formula and rest assured we are not contributing to eczema. Allergenic foods in infancy? For decades, we as pediatricians used to say that we should avoid giving kids eggs until age 2 years old and seafood and peanuts until age 3 years old but now we no longer think this is the case. There is no evidence that delaying the introduction of allergenic foods, including peanuts, eggs, and fish, beyond 4 to 6 months of age prevents atopic disease, and in fact the new thoughts in pediatrics is that early introduction of peanuts may prevent peanut allergy. We advise consulting your pediatrician about these sorts of feeding issues. Hygiene Hypothesis and What Causes Eczema in Babies In the late 1980s, people began to discuss the \u201chygiene hypothesis.\u201d It was suggested that less exposure to germs led to not allowing the immune system to mature adequately. So, the cleaner things were kept for young children in western cultures, the more chances that a child will get asthma, allergies, and eczema.\u00a0 There are now almost 30 years of studies looking at environmental exposure to germs at a young age and how it may help reduce the chances of being affected by atopic dermatitis.\u00a0 Specifically, studies show that kids that attend day care at an early age, and farmers kids who are exposed to benign germs from livestock may have less eczema. Other causes for eczema in babies This article on causes of eczema in babies would be incomplete if we did not mention a molecule present in skin that is sometimes missing. There are many, many components of the skin barrier. One of the most studied is Filaggrin. This protein and its derivatives help make what is caused Natural Moisturizing Factor (NMF). Loss of filaggrin can lead to a poorly formed stratum corneum (top layer of skin), and make the skin prone to water loss. If the skin barrier is not fortified appropriately any environmental substances can begin to trigger abnormal immune responses. People with Filaggrin mutations may have eczema develop at a young age. Other genes also play a role in epidermal barrier function but are beyond the scope of this article.\u00a0 Learn more about why babies get eczema as we continue to dive into this important topic.