|MadSci Network: General Biology|
If Becky is referring to nasal drainage this is the explaination: The fluid in our sinuses is normally clear and colorless. When someone has a sinus infection it may become cloudy due to white blood cells collecting there to fight the infection. The abnormal colors observed are a result of the bacteria and the toxins they make. Different bacteria or viruses produce substances with different characteristics. Also, if there is nasal or sinus trauma (like when we blow our nose too hard) there may be blood in this fluid.
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