What could hard, solid phlegm be a symptom of?

The phlegm can be from environmental irritants that you are breathing in or an upper respiratory infection. If it is an infection and you are feeling good otherwise, then your body is handling the infection well.The consistency is related to how much fluid you are taking in. If you are a little dehydrated, your body produces thicker mucus. Drink more water, the secretions will loosen and clear from your lungs faster.