How to differentiate between cough due to lung heat and cough due to lung cold

Heat-phlegm cough and cold-phlegm cough differ significantly in symptoms due to different pathogenic factors, with core distinctions mainly found in etiology and pathogenesis, characteristics of sputum, accompanying symptoms, sensations in mouth and nose, tongue coating, and pulse manifestations. A detailed analysis is as follows:

1. Etiology and Pathogenesis: Heat-phlegm cough results from external invasion of wind-heat pathogens into the lung defense system or internal accumulation of heat stagnating in the lungs; its core mechanism involves heat pathogens impairing the lungs. Cold-phlegm cough arises from external constraint of wind-cold pathogens on the lung defense or internal generation of cold pathogens attacking the lungs; its core mechanism involves cold pathogens constricting the lungs.

2. Sputum Characteristics: Heat-phlegm cough is typically characterized by yellow, thick, sticky sputum that is difficult to expel, sometimes accompanied by blood streaks; cold-phlegm cough features white, thin, watery sputum that is abundant and easily expelled, often appearing frothy.

3. Accompanying Symptoms: Heat-phlegm cough is commonly associated with marked fever, mild aversion to wind, sore and swollen throat, dry mouth and tongue, dry stools, and dark yellow, scanty urine—typical signs of internal heat. Cold-phlegm cough is more likely to present with prominent chills, mild fever, absence of sweating, body aches, nasal congestion, and clear, runny nasal discharge—typical signs of cold.

4. Sensations in Mouth and Nose: In heat-phlegm cough, the mouth and nose often feel dry and hot, with warm exhaled breath, and patients may experience dryness and a desire to drink cold water. In cold-phlegm cough, the mouth and nose tend to feel cool, with little or no thirst, or only a preference for small amounts of warm fluids.

5. Tongue Coating and Pulse: Patients with heat-phlegm cough typically exhibit a thin yellow or greasy yellow tongue coating, a red tip of the tongue, and a floating-rapid pulse. Those with cold-phlegm cough show a thin white tongue coating and a floating-tight pulse. These tongue and pulse findings are key diagnostic indicators.

When differentiating between the two types, a comprehensive evaluation of all symptoms should be performed to avoid misdiagnosis based on isolated signs. Treatment must be symptom-targeted and strictly follow medical guidance to ensure safety and effectiveness.