正常人的體溫會不停的變動，六歲以下的嬰兒每天體溫只會有少許的變動，六個月至兩歲的幼兒每天約有一度的變化。直至到六歲時，體溫變化會增至每日約兩度，成人的體溫則變化不大。但女性於經期時體溫會增加一度或以上，我們的體溫於黃昏時升到最高。體溫亦會因活動、情緒、飲食、衣服、藥物、室溫和高濕度，兒童最易受這些因素所影響。
正常的體溫應為36.8至37.5℃，發燒並不是疾病，更不是敵人，它是人體重要的自然防衛反應，發燒是一個訊號來告訴我們身體正處於戰鬥狀態。當白血球細胞打仗時，便會發出化學物質：致熱原，這些致熱原刺激腦部的體溫調節器：視床下部，再啟動體熱而提升體溫來對付入侵者，很多的微生物於溫度約38.88℃便會死亡，而病毒於37.77至38.88℃時便不能繁殖。除此之外，每當體溫升高一度F時，白血球細胞的活動能力就增強一倍，如果當體溫是40℃時，那時白血球的活動能力比36.66℃時就增強了64倍！抑制發燒只會對免疫系統做成傷害。
自然療師認為發燒是因為體內積聚了毒素而形成的，發燒作用於顯示身體有某些急性的疾病外，還同時試圖將體內聚積的毒素排出體外。如果發燒能自然地進行，這人的健康狀況應比從前更好，這便是身體的自然排毒現象。
現代的醫學只懂得用藥物壓制發燒，體溫雖然降低了，但後果只會比發燒前更嚴重，因為藥物抑制了身體用發燒來排除體內毒素的天然方法，到最後毒素只是仍然滯留於體內。
發燒時，斷食是幫助體內清除毒素的最好方法，發燒時並不需要任何的食物，因為此時體內的能量正集中於排除體內積聚的毒素。而消化時身體是需要運用相當的能量，這樣便會將某部份用作排毒的能量轉移到消化系統，便會減弱排毒的果效。相反，持續的飲用大量的飲料卻對發燒很有幫助，可防止脫水現象的出現，而鮮榨蔬果汁更可增強排毒果效。草本茶如西洋蓍草或薑等有助排汗而幫助散熱，於胸膛或半邊臀部施予熱敷，及用溫水濕敷全身。不要使用冷敷，這只會使毛孔收縮而阻礙身體透過毛孔而散熱。當體溫開始回復正常及舌頭轉回粉紅色時，便可回復進食。
很多人以為發燒會燒壞腦，其實不然，除非當體溫升至42℃。如果讓發燒自然地進行而患者並沒有過量地穿著厚衣或其它環境因素，體溫很少達至40.55℃。而當體溫達至41.11℃時，腦部的體溫調節器便會開始工作，使體溫停止繼續上升。既然發燒不會傷到大腦，那麼為什麼一些原本正常的小孩，在某次的高燒後，就顯得非常不靈光或幾近白癡狀態呢？的確，偶然會有這類的個案發生。但並不是由高燒造成，而是原本就因腦炎、腦膜炎或其它因素等所造成的大腦傷害，與高燒本身是兩回事。事實上應該是說疾病本身沒有獲得適當的控制，才會出現併發症的，至於「燒」只是症狀而已，根本不是引起併發症的原因。
千萬不要將阿司匹靈給予正在發燒的兒童服用，這會引致免疫系統有不良反應，導致產生一種致命的自我免疫系統疾病：雷氏症候群。
Normal body temperature is a moving target. In children younger than six months of age, the daily variation is small.
In children 6 months to 2 years old, the daily variation is about 1 degree. Daily variations gradually increase to 2 degrees per day by age six. Body temperature varies less in adults. However, a woman's menstrual cycle can elevate temperature by one degree or more. Your body temperature is usually highest in the evening. It can be raised by physical activity, strong emotion, eating, heavy clothing, medications, high room temperature, and high humidity. This is especially true in children.
The temperature in health ranges between 98.4°F and 99.5 °F. Fever is not an illness. Far from being an enemy, it is an important part of the body's defense against infection. A fever is a signal that a battle is going on in the body. As the army of white blood cells battles, the cells release chemicals called pyrogens. These pyrogens activate the hypothalamus, a part of the brain that serves as the body’s thermostat regulator, to turn on the internal heat and raise the body temperature to fight off invaders. Many microbes start to die at around 102 °F and viruses can’t multiply at temperatures between 100 and 102 °F. Moreover, for every degree of temperature rise in your body, the speed at which your white cells can travel to the disease and their effectiveness is doubled. If you have a 104 °F fever, the speed at which your white blood cells can move is 64 times faster than at a normal temperature of 98 °F. Suppressing a fever impairs the immune system.
Naturopathy believes that fever develops in a body only when the system is in a condition of internal uncleanliness. Fever is a direct manifestation of an acute disease but at the same time it represents the effort of the body to expel the poisons which have accumulated in it. If the fever is allowed to run its course in a natural manner, the sufferer would be in better health than before after the body has thrown off the affliction. It is nature’s way of spring-cleaning of the body.
Modern medicine seeks to cure the fever with drugs but it succeeds only in suppressing it. The administration of drugs and the temperature may go down but in umpteen cases maladies more serious than fever result because the drugs suppress the ejection of the poison which nature tried to by means of a rise in the temperature of the body.
The first thing that should be done to help the body to carry out the spring-cleaning is to make the sufferer fast. The system of a person suffering from fever does not need any food because all his energies are directed towards ejecting the poisons accumulated in the body. If the body has to divert a part of those energies towards the digestion of food which in most cases is forced on the patient because the physician thinks that his strength is to be maintained, the only result is that the course of nature is obstructed creating complications. Regular water intake is important to prevent dehydration. Fresh juices help the body eliminate toxins. Herbal tea such as yarrow or ginger helps induce a sweat for heat dissipation. Apply a hot compress to the chest or buttocks and sponge whole body with warm water. Denial of food to the patient may have to be continued for a week. Only when the temperature has dropped to 98 °F and the tongue of the patient is a healthy pink should he be given food.
Many parents fear that fevers will cause brain damage. Brain damage from a fever generally will not occur unless the fever is over 107.6°F (42°C). Untreated fevers caused by infection will seldom go over 105°F unless the child is overdressed, or trapped in a hot place. The brain's thermostat will stop the fever from climbing above 106°F.
Some parents fear that fevers will cause seizures. For the great majority of children, this is not the case. However, febrile seizures do occur in some children. Once a child is already known to have a high fever, a febrile seizure is unlikely with the current illness. In any event, simple febrile seizures are over in moments with no lasting consequences.
Never give aspirin to a child whoa has a fever. This can cause an immune reaction, leading to the development of Reye’s syndrome, a potentially fatal autoimmune illness.
Reference 參考資料：
Hackensack University Medical Center's website
American College of Osteopathic Family Physicians http://www.acofp.org/member_publications/1003_1.html
http://naaritoday.com/health/alternativetherapies/fever.html
