Table 2.

Environmental risk factors for atopic dermatitis (AD)

Factor	Associated effect on AD risk
Urban versus rural dwelling	Increased risk for AD with urban dwelling [12, 19]
Socioeconomic status	Increased risk for allergic sensitization in children with increasing parental socioeconomic status/goods ownership [38]
Education level of parents	Increased risk for allergic sensitization and AD in children with increasing parental education level [38, 51]
Climate	Increased risk for AD in colder climates; decreased risk for AD with UV light exposure [12, 19]
Pollution	Increased risk for AD with exposure to pollution [12] and with maternal exposure to active or passive cigarette smoking during prenatal period [39]
Family size	Increased risk for AD with smaller family size [19]
Personal hygiene, sanitation	Increased risk for AD with better personal hygiene in early childhood [40]; increased risk for allergic sensitization/AD in children with access to sanitation (modern toilets, piped drinking water) [38, 51]
Antibiotic use	Increased risk for AD with antibiotic exposure in prenatal period [39] and during the first year of life [41]; decreased risk with antibiotic exposure after the first year of life [39]
Breastfeeding	Decreased risk for AD in infants with familial history of AD [19]
Farm and animal exposure	Decreased risk for AD with frequent prenatal exposure to farm animals; most protective when compounded with direct exposure [42]; potential decreased risk with postnatal exposure to furry pets, particularly dogs [39, 43, 44]
Intestinal microflora	Decreased risk for AD with greater diversity of gut microflora in infancy [45]; decreased risk for allergic sensitization/AD with colonization favoring lactobacilli and bifidobacteria in infancy or childhood [46–49]