A fever of unknown origin is a temperature that reaches 101°F (38.3°C) on and off for at least 3 weeks with no known cause. Fever is a symptom of another condition, so your doctor will do tests to narrow down the causes and determine how to treat the underlying illness.
Your doctor may prefer not to give you medication while your fever remains undiagnosed. Research suggests that fever helps fight infection. Treating the fever without knowing the cause might reduce your body's ability to deal with the possible infection. However, doctors will prescribe drugs to reduce fever in children who suffer seizures caused by fever (febrile seizures). Because a higher temperature increases your need for oxygen, your doctor may prescribe fever-reducing medicines if you have heart or lung problems.
Fever is a symptom of more than 200 conditions. In children, infection accounts for about 50% of cases of fever of unknown origin, while inflammatory and malignant disease account for 5 to 10%. In adults, infections only account for 16% of cases, followed by tumors and noninfectious inflammatory diseases, such as rheumatoid arthritis. However, in up to half of cases in adults, no cause is found. Doctors can use a series of tests to narrow down the list of possible reasons for a high temperature.
A health care provider trying to diagnose the cause of a fever of unknown origin must look for every possible clue. The provider may ask you questions about:
Your provider will also examine you closely, paying particular attention to your skin, eyes, nails, lymph nodes, heart, and abdomen. The provider will also take blood and urine samples. You may have an ultrasound, computed tomography (CT) scan, magnetic resonance imaging (MRI), and Positron Emission Tomography (PET). If the cause of the fever is still unknown, your provider may want to inject you with "labeled white blood cells." These are white blood cells that contain a harmless radioactive compound. Once injected, the white blood cells travel to infected parts of your body. The radioactivity allows your provider to see on an x-ray where the cells have moved. This may show the location of the infection responsible for your fever. If that test shows no results, your provider may want to perform minor surgery to take biopsy samples of, for example, your liver or bone marrow.
Your doctor will advise you to rest and drink plenty of fluids. You may be asked to stop taking medications for other ailments, because those medications may be causing your fever. If you have a heart or lung problem, or in the case of a child who has seizures as a result of fever, your doctor will probably prescribe over-the-counter remedies to bring the temperature down.
General immune support with nutrition and herbs may alleviate fevers. Most natural medicine practitioners will treat fever as a sign that the body is trying to heal itself, rather than as an illness. In addition, most natural therapies attempt to support the body's own healing processes rather than suppress the fever. It is important to speak to your medical doctor about any natural therapies you may be considering. Prolonged fever can be dangerous, and some natural therapies and conventional medications can have dangerous interactions. If you are pregnant, or thinking of becoming pregnant, do not use any complementary and alternative therapies (CAM) unless directed to do so by your physician.
These nutritional tips may help improve immunity:
You may address nutritional deficiencies with the following supplements:
Herbs are a way to strengthen and tone the body's systems. As with any therapy, you should work with your doctor to choose the safest, most effective herbal therapies before starting treatment. You may use herbs as dried extracts (capsules, powders, or teas), glycerites (glycerine extracts), or tinctures (alcohol extracts). Unless otherwise indicated, make teas with 1 tsp. herb per cup of hot water. Steep covered 5 to 10 minutes for leaf or flowers, and 10 to 20 minutes for roots. Drink 2 to 4 cups per day. You may use tinctures alone or in combination as noted.
The following herbs may help reduce fever and improve immune response:
Although few studies have examined the effectiveness of specific homeopathic therapies, professional homeopaths may consider the following remedies for the treatment of fevers based on their knowledge and experience. Before prescribing a remedy, homeopaths take into account a person's constitutional type, includes your physical, emotional, and psychological makeup. An experienced homeopath assesses all of these factors when determining the most appropriate treatment for each individual.
Acupuncture may help support immune function.
Fever can be dangerous if you are pregnant. Speak with your physician.
Belhassen-Garcia M, Velasco-Tirado V, Lopez-Bernus A, et al. Fever of unknown origin as the first manifestation of colonic pathology. Clin Med. 2013;13(2):141-5.
Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas and Bennett's Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2009.
Bleeker-Rovers CP, van der Meer JW. Diagnostic approach to fever of unknown origin. Ned Tijdschr Geneeskd. 2008;152(15):869-73.
Bleeker-Rovers CP, van der Meer JW, Oyen WJ. Fever of unknown origin. Semin Nucl Med. 2009;39(2):81-7
Bryan CS, Ahuja D. Fever of unknown origin: is there a role for empiric therapy? Infect Dis Clin North Am. 2007;21(4):1213-20.
Cabrera C, Artacho R, Gimenez R. Beneficial effects of green tea -- a review. J Am Coll Nutr. 2006;25(2):79-99.
Chen Y, Zheng M, Hu X, et al. Fever of unknown origin in elderly people: a retrospective study of 87 patients in China. J Am Geriatr Soc. 2008;56(1):182-4.
Cunha BA. Fever of unknown origin: clinical overview of classic and current concepts. Infect Dis Clin North Am. 2007;21(4):867-915.
Diogo M. Adult-onset still disease as the cause of fever of unknown origin. Acta Med Port. 2010;23(5):927-30.
Gonclaves C, Dinis T, Batista MT. Antioxidant properties of proanthocyanidins of Uncaria tomentosa bark decoction: a mechanism for anti-inflammatory activity. Phytochemistry. 2005;66(1):89-98.
Holder BM. Fever of unknown origin: an evidence-based approach. Nurse Pract. 2011;36(8):46-52.
Jun-Cai TU, Ping Z, Xiao-Juan LI, et al. Clinical Etiologies of Fever of Unknown Origin in 500 cases. Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2015;37(3):348-51.
Keidar Z, Gurman-Balbir A, Gaitini D, et al. Fever of unknown origin: the role of 18F-FDG PET/CT. J Nucl Med. 2008;49(12):1980-5.
Knockaert DC. Recurrent fevers of unknown origin. Infect Dis Clin North Am. 2007;21(4):1189-211.
Norman DC, Wong MB, Yoshikawa TT. Fever of unknown origin in older persons. Infect Dis Clin North Am. 2007;21(4):937-45.
Petelin A, Johnson DH, Cunha BA. Fever of unknown origin (FUO) due to systemic lupus erythematosus (SLE) presenting as pericarditis. Heart Lung. 2013;42(2):152-3.
Rigante D, Esposito S. A roadmap for fever of unknown origin in children. Int J Immunopathol Pharmacol. 2013;26(2):315-26.
Ritz N. Fever without focus and fever of unknown origin in childhood. Praxis. 2013;102(3):157-64.
Seashore CJ. Fever of unknown origin in children. Peditr Ann. 2011;40(1):26-30.
Tolia J, Smith LG. Fever of unknown origin: historical and physical clues to making the diagnosis. Infect Dis Clin North Am. 2007;21(4):917-36.
Turkulov V. Fever of unknown origin in elderly patients. Srp Arh Celok Lek. 2011;139(1-2):64-8.
Vertenoeil G, Servais S, Beguin Y. How to explore a fever of unknown origin in adult patients? Rev Med Liege. 2012;67(7-8);391-7.
Yoon JH, Baek SJ. Molecular targets of dietary polyphenols with anti-inflammatory properties. Yonsei Med J. 2005;46(5):585-96.
Reviewed By: Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.
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