What causes a sudden unpleasant odor under one armpit when touched, and what should be done about it?
Nov 28, 2025
Source: Cainiu Health
Dr. Liu Wenmin
Introduction
Sudden odor under one armpit may be caused by untimely cleaning, localized sweat accumulation, bacterial folliculitis, infected sebaceous cyst, or mild axillary bromhidrosis. It is recommended to seek medical attention promptly, identify the underlying cause, and then improve the condition through general measures or medication as directed by a physician. In daily life, choose loose, breathable cotton clothing and avoid keeping the armpits in a hot and humid environment for prolonged periods.
Under normal circumstances, sudden odor in one armpit may be caused by untimely cleaning, localized sweat accumulation, bacterial folliculitis, infected sebaceous cysts, or mild axillary osmidrosis. It is recommended to seek medical attention promptly, identify the underlying cause, and then improve the condition under a doctor's guidance through general management, medication, or other treatments. A detailed analysis is as follows:
1. Untimely cleaning: If sweat and sebum on one side of the armpit are not cleaned promptly, bacteria can break down secretions and produce odor. Wash the armpits daily with warm water, paying special attention to the affected side. After washing, dry thoroughly with a clean towel and keep the armpits dry.
2. Localized sweat accumulation: During intense exercise or in high-temperature environments, sweat glands on one side of the armpit may become overactive, and prolonged retention of sweat can lead to odor. Change into breathable clothing promptly after exercising, avoid wearing tight synthetic fabrics, and consider using a gentle antiperspirant to reduce sweat secretion.
3. Bacterial folliculitis: Hair follicles on one side of the armpit may become infected with Staphylococcus aureus, causing inflammation that leads to abnormal secretions and odor, often accompanied by small red papules. Patients should follow medical advice to apply topical medications such as mupirocin ointment, fusidic acid cream, or compound polymyxin B ointment, and avoid squeezing the lesions to prevent spreading the infection.
4. Infected sebaceous cyst: A blocked sebaceous gland duct on one side of the armpit may form a cyst, which develops noticeable malodor upon secondary infection, along with local redness, swelling, and pain. Patients should take oral antibiotics as prescribed, such as cefaclor capsules, amoxicillin-clavulanate potassium tablets, or roxithromycin capsules, to control the inflammation.
5. Mild axillary osmidrosis: Abnormal secretion from apocrine glands on one side of the armpit can be broken down by bacteria to produce odor, which worsens after physical activity. Under medical guidance, patients may use agents such as methenamine solution, formaldehyde solution, or aluminum chloride solution. In severe cases, minimally invasive surgery can be performed to destroy apocrine gland tissue and reduce secretion.
In daily life, choose loose-fitting, breathable cotton clothing to prevent the armpits from remaining hot and humid for extended periods. Maintain a light diet and reduce intake of pungent foods such as garlic and onions. Regularly trim underarm hair to minimize bacterial adhesion and growth, helping to alleviate odor issues.
