The blue light that emits from our phone, laptop and other devices can have a negative impact on sleep, skin, and mood, Vogue reports.

Just like your physics professor said, light rays come in different colors, with each wave frequency corresponding to a color, and each color carrying its own effects. Our phone, laptop and tablet screens emit blue light, which has been shown to have a negative impact on sleep, skin and mood.

The why, in a word, is hormones. The waxing and waning of hormones such as cortisol are meant to generate a circadian rhythm that gives us energy during the day and helps us wind down at night. But a specific strain of blue light in the range of 420 to 480 nanometers from artificial devices such as phones disrupts natural cortisol cycles, depressing our energy during the day and amping us up at night.

Blue light also has the ability to penetrate deep into our skin, triggering free radicals and inflammation to generate hyperpigmentation and age spots. Some studies also suggest that blue light damages a molecule in the eye called the retinal, setting off a chemical reaction that may be toxic to the retina’s cells.

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