Sweating During Flu: Clinical Significance
Sweating when you have the flu is a normal part of uncomplicated influenza infection and indicates your body's fever response—specifically, "hot and moist skin" is a characteristic clinical finding during the acute phase of illness. 1
What Sweating Means in Flu
Normal Clinical Presentation
Sweating is an expected finding in uncomplicated influenza, described in clinical guidelines as "hot and moist skin" that occurs alongside the toxic appearance, flushed face, and injected eyes during the initial stages of infection. 1
The sweating accompanies fever, which is the paramount symptom of influenza, typically ranging between 38-40°C (100.4-104°F), though it may reach 41°C (105.8°F). 1
Fever peaks within 24 hours of symptom onset and typically lasts for three days (range 1-5 days), with the sweating being part of your body's thermoregulatory response. 1
What It Does NOT Mean
Sweating alone does not indicate complications or worsening disease—it is simply part of the normal fever pattern in influenza. 1
The presence of sweating should not be confused with signs of serious complications, which would include respiratory distress, persistent high fever beyond 5 days, chest pain, or altered mental status. 1
When to Be Concerned
Red Flags Requiring Medical Attention
While sweating itself is benign, watch for these concerning features that indicate potential complications:
Respiratory complications: Development of productive cough with chest tightness, difficulty breathing, or wheezing beyond the typical dry cough. 1
Prolonged or recurrent fever: Fever lasting beyond 5 days or fever that resolves then returns (suggesting secondary bacterial pneumonia, which typically occurs 4-5 days after illness onset). 1
Severe symptoms: Toxic appearance that worsens rather than improves, confusion, severe chest pain, or inability to maintain hydration. 1
Expected Disease Course
Uncomplicated influenza typically resolves in 7 days, though cough and malaise may persist for more than 2 weeks. 1, 2
The sweating and fever should improve within 3-5 days as part of the natural resolution of illness. 1
Adults remain infectious from the day before symptom onset through approximately 5-6 days after illness begins. 2
Clinical Pitfall to Avoid
Do not assume sweating means "breaking the fever" in a positive sense—while it accompanies fever, it's simply a physiologic response and doesn't necessarily indicate imminent recovery or that the illness is less severe. 1
The key is monitoring the overall clinical trajectory: improvement in constitutional symptoms (malaise, myalgia, headache) alongside fever resolution indicates uncomplicated recovery. 1, 2