After showering, there's a slight sour smell under the armpits.

A slightly sour odor under the armpits after bathing may be caused by physiological factors as well as pathological conditions such as bromhidrosis (body odor) and trichomycosis axillaris. Most cases can be relieved through general management, medication, or surgical treatment. The specific analysis is as follows:

1. Physiological Causes

If a person is emotionally agitated or in a high-temperature environment, it may lead to excessive sweating under the armpits. Symptoms usually gradually improve once emotional state or ambient temperature is stabilized.

2. Pathological Causes

1) Bromhidrosis (Body Odor)

Bromhidrosis is a common skin condition primarily caused by secretions from apocrine glands in the armpits. Bacteria on the skin break down these secretions, producing an unpleasant smell. Individuals with this condition may experience the described symptoms. In such cases, treatment under medical guidance—such as excision surgery for bromhidrosis—is recommended.

2) Trichomycosis Axillaris

Trichomycosis axillaris is mainly caused by infection with *Corynebacterium tenuis*. Contributing factors include obesity and prolonged exposure to warm, humid environments. Affected individuals may develop the aforementioned odor, though often without noticeable symptoms. Treatment may involve topical medications such as erythromycin ointment, fusidic acid cream, or sulfur ointment, used according to a doctor's advice.

Besides the above relatively common causes, this condition could also result from folliculitis, hidradenitis, tinea corporis (ringworm), and other conditions. If significant discomfort occurs, it is important to promptly visit a reputable hospital to determine the exact cause and receive appropriate, targeted treatment.