There are more sensible ways to dry excess phlegm in the sinuses. Herbs are more gentle. Also, it is understood that they should be taken for a limited period of time, while the symptoms persist. If a person took drying herbs (for example, those that increase sweating) for a long time, they could provoke dry cough, thirst, or dehydration symptoms. The following herbs should be used no longer than a few days, or combined with cooling, moistening herbs.