The skin is a selectively permeable membrane. This means the body has some control over what substances pass through the skin’s surface, and what substances are ushered out through sweat. Your baby’s skin becomes more selectively permeable as she grows, but since the most marked difference in thickness seems to occur around the 30th week of gestation, the skin of premature babies can be so permeable that the baby can become easily dehydrated, infected and even accidentally poisoned. To prevent toxic exposure, be sure to avoid pollutants in the environment like chlorine from tap water and contaminants like 1,4-dioxane found in personal care products made from petroleum byproducts such as mineral oil.
Different skin types vary significantly in permeability – natural features, like thickness and skin color are important factors, as well as environmental considerations like humidity, temperature and level of hydration. Darker skin tends to be less permeable because it is thicker due to more layers of horny cells (the outermost layer of densely packed skin cells that eventually turn into keratin.)
As the skin thickens, its ability ward off unwanted ecological intruders improves, but it is not necessarily more effective at keeping toxins at bay. The skin’s job to determine what substances should and should not pass through into the body has become exponentially more difficult. Since World War II, more than 87,000 new chemicals have been placed on the market, and more than 2,400 new chemicals are introduced yearly. Most of these are not properly tested for toxicity to the environment or human tissue before they are put into use.
The number of newborns experiencing skin disorders is on the rise, and the transdermal capabilities of skin can allow contaminants to enter the body at an alarming rate. Because the skin is susceptible to all kinds of environmental toxins, from ammonia in cleaning supplies to off-gassing from foam mattresses, parents need to be especially careful not to put toxins directly on the skin through toiletry products, bedding, and clothing. This awareness becomes even more important when deciding how to treat compromised skin that is dry or presents with a rash.