My saliva is mostly brown when i wake up from sleep. it's been occurring since childhood and i am 32 now. sometimes i think it's because i don't brush before bed. but it still happens after brushing before bed. what could be the cause please?

Acid reflux is a common cause of morning brownish saliva, but it can also come from nasal, mouth and teeth causes. Don' t eat anything 2 hours before bedtime. Try sleeping on your left side. Sleep with your chest higher than your stomach. You might wish to be evaluated and advised by an ENT specialist.

A number of causes including smoking, gum disease, dehydration, GERD known as acid reflux disease, liver diseases, and porphyria. Consultation with your primary care physician would be the first step to sort out cause(s).