Numerous other diseases and conditions can also cause an itchy rash — from scabies to viral infections like chickenpox to bacterial infections like impetigo. But unlike these other examples, eczema is not caused by tiny mites or microbes that can be passed from person to person. “Atopic dermatitis, the most common type of eczema, is not contagious,” explains Kanwaljit K. Brar, MD, a pediatric allergist and immunologist at NYU Langone in New York City. Instead, atopic dermatitis is a chronic inflammatory skin condition, in which an immune system reaction causes symptoms to develop. The condition is associated with a wide range of potential risk factors, but its specific cause in any given person is unclear. (1)
Patches of skin that are rough and leathery or scalySwollen skinSkin color changes (1)RashHivesIncreased lines on the palms of the hands and feetDry, pale patches on the face and upper armsSmall bumps on the upper arms and thighs (2)
Rather than a single factor being behind the development of atopic dermatitis, research suggests that eczema is a complex condition involving genetics, skin barrier function, allergies, immune system dysfunction, and environmental factors. (3,4) What’s more, the symptoms of atopic dermatitis typically arise from specific and varied triggers, including dry skin (from weather changes, for example), a wide range of irritants like common cleaning products and fabrics, and stress. (5) In fact, atopic dermatitis is often the start of the so-called “atopic march,” in which a person then develops food allergies, hay fever, and asthma. It’s estimated that up to 60 percent of people with atopic dermatitis develop asthma or hay fever and up to 30 percent have food allergies. As with other allergic disorders, atopic dermatitis tends to run in families. Having a parent with atopic dermatitis, hay fever, or asthma increases a person’s risk of getting the skin condition. (6) But, Dr. Brar notes, atopic dermatitis can also develop without a demonstrated family history for atopic conditions. Research suggests that a number of genes are associated with the development of atopic dermatitis. One gene with the strongest association is FLG, which encodes a protein, called filaggrin, that is important for creating a strong skin barrier to keep water in and foreign substances out. About 20 to 30 percent of people with atopic dermatitis have a mutated or altered FLG gene, compared with 8 to 10 percent of people without atopic dermatitis, according to the National Library of Medicine. Other skin-related genes, such as SPINK5/LEKT1, are also associated with atopic dermatitis. In very rare cases, atopic dermatitis may arise from the mutation of a single gene: CARD11. A mutation in this gene can result in abnormalities in certain immune system cells. (4,6) Some research suggests that boys are more likely than girls to develop atopic dermatitis during infancy, and this pattern switches in adolescence. (7) Other research suggests that the prevalence of atopic dermatitis is higher among people of African ancestry. (8) Various other risk factors may also exist, though the data is still inconclusive. Specifically, these potential risk factors include:
Living in a developed country, a city, or a cold climateBeing born to a mother who is older (or later in her childbearing years)Being born into a higher social class or to parents with higher educationBeing born by Cesarean sectionBeing exposed to secondhand smokeBeing overweightHaving a high birth weightBeing treated with antibiotics in infancyBeing exposed to hard water in infancy
On the opposite side of things, some factors may be protective against atopic dermatitis. “Early moisturizer use in infants may reduce a person’s risk of atopic dermatitis,” Brar says. Others may include:
Being breastfed within the first three months of life (delayed weaning may increase risk)Being exposed to a child day-care settingDrinking unpasteurized farm milk during the first two years of lifeBeing exposed to farm animals (both during pregnancy and after birth)Having pets (specifically dogs) early in life (4,7,8,9)
But food allergies go hand in hand with atopic dermatitis, thanks to the atopic march. About 50 to 70 percent of children with early onset atopic dermatitis have one or more allergies, mainly food allergies, the most common of which are cow’s milk, hen’s eggs, and peanuts. (4) What’s more, becoming sensitized to food earlier in life may result in more severe atopic dermatitis later in life. And food avoidance (in the absence of an existing food allergy) increases the likelihood of developing new food reactions in the future. Food allergies can also make atopic dermatitis worse and can be triggers for symptom flares. That is, the skin lesions of atopic dermatitis are sometimes the result of an inflammatory response to the food allergens. (3,4,8) But some research suggests that high consumption of fish during pregnancy decreases the risk of atopic dermatitis in children, as does consuming fish late in infancy. (4) Research shows that cutting out specific foods from a person’s diet does not reduce atopic dermatitis symptoms unless that person has a known allergy to that food. And elimination diets can have negative consequences, such as nutritional deficiencies and the development of food sensitivites when those foods are reintroduced to the diet. (10,11) Eczema flares are caused by triggers. These eczema triggers may include a wide range of irritants, allergens, and other substances:
Soaps, detergents, shampoos, and dishwashing liquidsBubble bath liquidsMoldPollenPet danderDust mitesA hot or dry climateHigh or low humidityBacterial, viral, or fungal infections (5)Dust or sandCigarette smokePerfumes and cosmeticsWool or synthetic fabricsChemicals and cleaning solutions (12)Allergenic foods, such as milk, eggs, peanuts, soy, wheat, and fish (13)
