Sudden high fever of 39°C subsided quickly.

Generally, a sudden high fever of 39°C that quickly subsides may be caused by excessive emotional excitement, viral cold, autonomic nervous dysfunction, hormonal instability, infantile roseola, or other factors. If the patient experiences additional discomfort, prompt medical attention is recommended. Specific causes are as follows:

1. Excessive Emotional Excitement

When a person becomes overly emotionally excited, the sympathetic nervous system becomes activated, increasing the body's heat production, which can lead to a sudden rise in temperature to 39°C followed by rapid resolution. This is a normal physiological response and usually requires no special treatment; body temperature returns to normal once emotions stabilize.

2. Viral Cold

Viral infections are typically self-limiting. After a viral infection causes a cold, fever may occur. However, the body's immune system fights off the virus, leading to its natural clearance, which explains the aforementioned symptoms. Patients should increase fluid intake and, under medical guidance, take medications such as Amoxicillin Capsules, Siji Kangbingdu Oral Liquid, or Oseltamivir Granules for treatment.

3. Autonomic Nervous Dysfunction

Patients with autonomic nervous dysfunction may experience symptoms such as dizziness, chest tightness, diarrhea, numbness in limbs, and hot palms and soles. Once mental and emotional states stabilize, body temperature often improves accordingly, resulting in the aforementioned pattern. During this period, patients may also take neurotrophic medications as directed by a physician, such as Oryzanol Tablets or Vitamin B1 Tablets, to help alleviate symptoms.

4. Hormonal Instability

Menopausal women often experience hormonal fluctuations, which can cause bodily heat sensations and the symptoms described. However, once emotional balance is restored, the episodes of heat usually subside. Patients should maintain a positive mindset and avoid excessive anxiety. As prescribed, medications such as Estradiol Valerate Tablets orProgesterone Capsules may be used to improve symptoms.

5. Infantile Roseola

In cases of infantile roseola, body temperature may suddenly rise above 39°C and persist for 3–5 days, after which the fever resolves and a rash appears, with body temperature rapidly returning to normal. Generally, no specific treatment is required. Proper care during fever episodes includes increased fluid intake and tepid sponge baths. Additionally, medications such as Ibuprofen Suspension or Paracetamol Suspension Drops may be administered under medical supervision.

Besides the above, conditions such as tonsillitis, acute pneumonia, or systemic lupus erythematosus could also be responsible. If the underlying cause remains unclear, patients are advised to seek timely medical evaluation and treatment to prevent disease progression.