Why Do We Expose Jaundiced Babies to Light?

Skin Care
Babies suffering from jaundice are treated with light therapy. Read on to learn why the light on this baby is blue.

More than half of newborns will develop jaundice within their first week of life. This is termed physiological jaundice (meaning normal, or “to be expected”, as opposed to “pathological” jaundice). However, just as it plays a role in vitamin D metabolism, the skin also plays a pivotal role in solving the problem of jaundice.

What Is “Jaundice”?

Jaundice happens when the skin, mucus membrane, or eyes appear yellow in color as a result of increased levels of bilirubin in the blood, termed “hyperbilirubinemia.” Bilirubin is a product of the breakdown of the heme part of hemoglobin (we discussed this in an article on bruises). The liver is responsible for getting rid of bilirubin. In many newborns, especially preterm babies, this process has still not fully developed. In other instances, increased bilirubin could be a result of a disease process, such as blood diseases. To simplify things, jaundice turns “pathological” when bilirubin levels are higher and last longer.

[Read More: What’s in a Bruise?]

Why Must It Be Treated?

Bilirubin can cross into the brain and affect the central nervous system. The outcome can range anywhere from brain damage to various physical disabilities to severe motor and sensory dysfunction, and even death.

How Does Light Treat Jaundice?

Such a small change, such a huge difference

Excess bilirubin finds its way to the skin. When the newborn is exposed to light, bilirubin in the skin absorbs it and turns into a different isomer (an isomer is basically a compound that has been rearranged but still includes the same components). Unlike bilirubin, this new isomer (lumirubin) does not have to pass through the liver to be processed and excreted from the body. So the body can get rid of it much more easily than bilirubin! Light therapy starts working right away, ridding the body of a large amount of bilirubin in a much shorter time.

What Kind of Light Are We Talking About?

Not all light colors treat jaundice equally.

Light is actually made of of a spectrum of colors and some colors work better for treating jaundice than others. Blue light seems to affect bilirubin breakdown the most (between wavelengths of 460 and 490 nm).

Is Sun Exposure a Good Substitute?

As it turns out, sun exposure actually led us to understand the effect of light on bilirubin. An English nurse took a jaundiced newborn out for a walk one day and, upon returning, noticed that the skin that was exposed to the sun was not as yellow as it had been before.

The sun is very efficacious in treating hyperbilirubinemia. The problem is that you can’t measure the exposure. How much is enough? How much is too much? After all, we don’t want to risk a sun burn. Still, it remains a valid and cheap alternative, especially in poorer regions where finding light therapy is not easy.

Are there complications?

Quite rarely. But babies with a family history of porphyria, where the heme in hemoglobin is not made properly, should not have light therapy. There is some research linking light therapy to a possible increase in the incidence of moles later in life, but further work is needed to obtain conclusive evidence in that regard.

[Read More: A Look at Babies’ Skin and Skin Care]

Why are the baby’s eyes covered during light therapy?

Light at this intensity and duration could harm the retina, especially in a newborn and preterm baby.

Bottom line

It really is amazing how something as simple as exposure to light can prevent the serious, and sometimes deadly, complications of raised bilirubin.

Thank you for reading!


MJ. Maisels et al. Phototherapy for Neonatal Jaundice. The New England Journal of Medicine 2008; 358: 920-8.

TWR. Hansen. Phototherapy for Neonatal Jaundice: Therapeutic Effects on More than One Level? Seminars in Perinatology 2010; 3: 231-4.

Z. Csoma et al. Neonatal Blue Light Phototherapy and Melanocytic Nevi: A Twin Study. Pediatrics 2011; 128 (4): e856-65.

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