Causes of fever without infection

Fever is a common symptom of many medical conditions, and while infections are a frequent cause of fever, there are various other non-infectious causes of fever. Some of these include:

1. Inflammatory Conditions: Autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and inflammatory bowel disease can lead to fever as the body's immune system mistakenly attacks healthy tissues.
2. Heat Exhaustion and Heat Stroke: Excessive exposure to hot weather or physical exertion can lead to elevated body temperature.
3. Medications: Some medications, such as antibiotics, antipsychotics, and anti-seizure drugs, can cause drug-induced fever as a side effect.
4. Malignancies: Certain cancers, such as lymphomas and leukemias, can cause fever as a paraneoplastic syndrome, where the body reacts to the presence of the cancer.
5. Autoinflammatory Disorders: Conditions like familial Mediterranean fever (FMF) and periodic fever syndromes are characterized by recurrent fever episodes due to genetic abnormalities in the innate immune system.
6. Organ Inflammation: Inflammatory conditions affecting specific organs, like hepatitis or pancreatitis, can result in fever.
7. Endocrine Disorders: Thyroid storms in hyperthyroidism or adrenal crises in Addison's disease can lead to fever.
8. Blood Clots: Deep vein thrombosis (DVT) and pulmonary embolism (PE) can sometimes cause fever as a result of the body's response to the clot.
9. Connective Tissue Diseases: Conditions like systemic sclerosis (scleroderma) can cause fever in addition to other symptoms.
10. Vaccination: After receiving some vaccines, mild fever can occur as a normal part of the body's immune response.
11. Hematologic Disorders: Conditions such as hemolytic anemia and sickle cell crisis can lead to fever.
12. Environmental Toxins: Exposure to certain toxins and chemicals can lead to fever, as the body tries to detoxify itself.
13. Stress and Anxiety: Severe emotional stress can sometimes lead to psychogenic fever, where the body temperature rises without an underlying medical cause.

It's important to note that fever is often a symptom of an underlying issue, and diagnosing the cause may require a thorough medical evaluation, which can include physical examination, medical history, blood tests, imaging studies, and sometimes further specialized tests. If you or someone you know is experiencing unexplained or persistent fever, it is advisable to seek medical attention to determine the underlying cause and receive appropriate treatment.