Malaise is a general feeling of physical discomfort or uneasiness.
What is going on in the body?
Malaise is often the first sign of an infection or other disease. Many people can "feel" an infection or disease starting because they develop the feeling of malaise. The causes of malaise can range from working out or studying too hard to cancer.
What are the causes and risks of the condition?
Almost any sudden illness and many chronic illnesses can cause malaise. The more common causes include:
lack of sleep or sleep disorders
infections, such as acute bronchitis, a common cold, the flu, or infectious mononucleosis
a low blood count, called anemia
hormone imbalances, such as a low thyroid hormone level, called hypothyroidism. Another example is low adrenal hormone levels, called hypoadrenalism.
depression or other psychological disorders
autoimmune disorders, which are conditions in which a person's immune system attacks his or her own body for no apparent reason. Examples of autoimmune diseases include systemic lupus erythematosus and rheumatoid arthritis.
toxin or chemical exposure, such as carbon monoxide or lead poisoning
medications, such as antihistamines, cancer chemotherapy, or certain medications used to treat depression and high blood pressure. Examples include atenolol, paroxetine, and diphenhydramine.
systemic disorders, such as heart, liver, lung, or kidney disorders
tumors or cancer, such as lung cancer or a blood cancer called leukemia
salt imbalances, such as a low sodium level or a high potassium level
chronic fatigue syndrome and fibromyalgia, two poorly understood conditions with no known cause. These conditions commonly cause malaise and make people feel weak and tired.
Other causes of malaise are also possible. Sometimes, the cause is unknown.