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Entering the world, a newborn baby utters a loud and distinct cry – a sign of health and vigor. This is a cry that new parents will quickly get used to in the coming days and weeks. But if you look closely, you will see that the cry of a newborn is a little different than that of an older infant: there are no tears.
Tears, of course, are necessary to protect the eyes and keep them moist. When we face extreme emotions such as sadness, anger or even happiness, we cry, said Sage Timberline, a pediatrician at Davis Children's Hospital at the University of California, Sacramento, California. This temporary stress triggers a fight or flight response that produces tears to better protect the eye. These emotional tears can also help release stress-inducing hormones that can accumulate during difficult times; it contributes to the relief that follows a good cry, she told Live Science.
Although a baby is born with lachrymal ducts, they are not yet fully developed. They produce enough tears to cover the eye and keep it moist, but not enough to form drops that run down the chubby cheeks. After three or four weeks, a baby's tear ducts are usually sufficiently mature to form tears associated with strong emotions, said Timberline.
Related: Why do babies cry in planes?
The newborn's eyes tend to be dry – just like his skin. Regardless of the temperature, a newborn baby barely sweats during the first two weeks of life. This is because the sweat glands are not yet fully functional.
Humans have two types of sweat glands, called eccrine and apocrine glands, both of which are formed in the newborn, even if they do not yet produce sweat. The apocrine glands secrete sweat through hair follicles but are not activated until hormonal changes occur during puberty. Although apocrine sweat is odorless at first, it can become smelly. It is filled with water and electrolytes as well as steroids, lipids and proteins – which bacteria can turn into odors.
Eccrine glands begin to form in the fourth month of pregnancy and appear first on the fetal palms and soles of the feet. By the fifth month, eccrine glands cover almost the entire body.
After the birth of a baby, the most active eccrine glands are those of the forehead, said Timberline. A short time later, a baby begins to sweat on his chest and limbs.
Because newborns can not sweat completely, they rely on caregivers to keep them cool. Watch for signs of overheating, including sweating (as newborns produce perspiration); skin hot and red; Rapid breathing; agitation; and a decrease in the activity of arms and legs, said Timberline. If your baby is too hot, simply remove a layer of clothing or use a fan to keep the air circulating.
But once these glands start to sweat, some parents worry that their baby will not sweat too much when it feeds or sleeps, said Katie Ellgass, pediatrician at Altford Pediatric Associates of Stanford Children's Health in Los Altos , in California. "Both actions are hard work," she told Live Science. "When it feeds, a baby is often close to his caregiver.The body heat is transferred.This is a sweatfest!"
Fortunately, sweaty babies are not usually a cause for concern, said Ellgass. Babies are screened for metabolic diseases and heart problems of the newborn. Therefore, as long as they gain weight, baby's sweat is … well, nothing transpires.
Originally published on Science live.
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