Because scientists have discovered that the same receptors that exist on the tongue to taste bitter substances are also found on the smooth muscle of the lungs. (scientificamerican.com)
On the other hand, babies show distinct displeasure if offered bitter substances. (carolinaparent.com)
The most important dandelion metabolites are bitter substances which are especially found in a milky sap called latex, a substance found in almost ten percent of all flowering plants. (sciencedaily.com)