First of all, it’s important to know that blue light is entirely natural. It’s part of the visible light spectrum and we need it in our lives – it helps to regulate our body clock (or circadian rhythm). That’s the internal ‘mechanism’ that makes us feel sleepy at night, and wake up in the mornings.
Our daily rhythms are influenced by a hormone called melatonin. The levels of melatonin in our bodies are lowest early in the morning – so we feel awake and alert. Our melatonin levels rise during the day until we go to bed. Anything that interferes with our body clock can cause issues including insomnia, fatigue and drowsiness. Blue light actually suppresses the production of melatonin, making us feel unusually alert and awake.
Whereas natural light is a ‘balance’ of all forms of visible light, the screens on phones, tablets and other devices produce mostly blue light. Looking at your phone late at night – like scrolling through social media after you’ve gone to bed – can cause you to feel more awake, just when you need a good night’s rest.