Generally when the body is not functioning properly, there are 2 reasons why. Either there is too much of something or not enough of something.
A couple easy examples:
When someone is very dehydrated the body will exhibit symptoms of thirst, headache, fatigue or hunger. Their body is in need of water. If the symptoms are due to dehydration, they will dissipate within a few minutes of drinking 8 ounces or more of water..
When someone has a hangover due to too much alcohol consumption they may exhibit a headache, nausea, fatigue and brain-fog. Their body has an excess of alcohol and their liver is struggling to process it. Generally, water, rest and time will address this symptoms. Additionally, ingesting some type of healthy fat will also support the liver’s recovery.
The same is true for many other "mild" symptoms which can be attributed to ones body having too much or not enough of something.
Sinus congestion and excessive mucus could be a reaction to a difficulty in digesting dairy products... Yes, it is not always a symptom of digestion when something is out of balance.
Interesting…. Some degrees of anxiety, constipation, certain types of heart palpitations and cravings for chocolate have been traced to a deficiency of magnesium.