A white booger contains white-colored mucus, snot or phlegm from the nasal passage. White mucus can signal a cold, but doctors advise patients not to depend solely on mucus color to diagnose bacterial or viral infections. Simple acts, such as drinking milk, can cause some individuals to produce white mucus.
Mucus ranges in color, and can be white, yellow, green or a reddish-brown. Green or yellowish-green mucus often develops as the result of a viral or bacterial infection, because neutrophils, or white blood cells, contain a green-colored enzyme. Most often, reddish or brown-colored mucus results from a nosebleed or smoking.
Healthy individuals produce mucus daily. Mucus actually contains antibodies that work to keep the body healthy from bacteria and viruses. An indication of illness is thick mucus.