What Causes Night Sweats?

Recently I have begun profuse night sweats, so much so that I must leave my bed unmade to let it dry. I have no other symptoms, except a vague pain in the left chest on deep inspiration and an occasional nonproductive cough. I have no fatigue, weight loss or other symptoms. I am 50, in good physical condition. As a child I took isoniazid for a positive tine test, and my PPD has always been very positive, so it will not be of diagnostic value. What should I do next?


The term "night sweats" describes the exact symptom you have. Night sweats are not simply sweating a lot at night, but literally drenching the bed. If you are a woman, night sweats (or their daytime version, hot flashes) may be your first symptom of menopause; in both cases, the profuse sweating follows a brief but intense wave of heat, usually in the face and chest. Infections, malignancy and other diseases can also cause night sweats. When night sweats are due to an infection, the sweating usually occurs as the body temperature drops suddenly after running a fever.

Infections causing night sweats are usually chronic, and they may have been present for quite a while before a person seeks medical care.

  • Tuberculosis (TB) is the classic cause, and the fact that you had a positive tine test is interesting. As I have mentioned on this site before, positive PPD (skin test for TB) and tine test signify that you were likely infected with the tuberculosis organism. At this stage, the immune system typically controls the infection and few if any symptoms develop. Then, later in life, the infection may reactivate, causing a chronic pneumonia with fever, night sweats, weight loss and cough. Sometimes the infection involves the lungs minimally, if at all. If you have had night sweats for more than a month or two without any other symptoms, tuberculosis would be less likely but not impossible.
  • Various fungal infections may also be associated with chronic night sweats. Histoplasmosis, an infection usually seen in the southeastern, mid-Atlantic and central United States, is one such illness. You are less likely to have histoplasmosis (or any other fungal infection for that matter) if you have been ill for more than a few months with no other symptoms.
  • Another possibility is an abscess (a collection of pus due to infection) in the liver or spleen. Such an abscess can cause fever and sweats without many other symptoms. There are several other infectious causes of fevers and night sweats, too many to detail here. However, if an infection is responsible for your illness, I would expect that you would eventually start having other symptoms that point to the specific diagnosis.
  • Non-infectious illnesses can cause night sweats as well. The first that comes to mind is a malignancy. The most common symptoms of lymphoma, a tumor of the lymphatic system, are swollen lymph nodes, often in the neck. In addition, some people also have fever, night sweats and weight loss. Several other malignancies and other diseases can lead to night sweats as well.
  • Finally, the vague chest pain you describe is somewhat concerning. When I see a patient with chronic fevers and night sweats, a single complaint such as chest pain usually points to the source of the fever.

What I suggest you do is the following. First, figure out how long you have had night sweats. If you have had them more than several months, infection is less likely but not ruled out. Check to see if you are having true fever. The best time to check is in the evening, around 6:00 p.m., the usual time of highest temperature and before your night sweats. Then, talk to your physician about what could be causing your night sweats. If you are really having chronic fevers, night sweats and chest symptoms, a physical examination and some testing are probably in order. A blood count could show evidence of an infection or malignancy. A chest X-ray and possibly a CT scan of the chest may show signs of tuberculosis, another infection or another chest abnormality responsible for your fever. If all these tests reveal nothing, a CT scan of the abdomen may show an abscess. I certainly do not think you need all these tests up front, but sometimes chronic fever requires quite a lot of testing to arrive at the correct diagnosis.


by Harold Oster