We all know the feeling well: that initial mild discomfort, the headache, the chills even on a hot day... We take our temperature and, indeed, there is the confirmation of what we already know: we have fever.
That elevation of body temperature is often the first sign of a cold, a sore throat, or any other incipient infection. The unmistakable announcement that we are sick.
But why does it occur? "Fever is one of the most important defense mechanisms that the body has," explains Manuel Mozota, spokesperson for the Spanish Society of General Practitioners and Family Medicine (SEMG).
It is one of the most effective responses we have to combat an infectious agent. Because it allows us to fight against it from different angles, he clarifies.
When a virus or bacteria enters the body, the immune system alerts the hypothalamus - the brain's 'thermostat' - that it is necessary to raise the body temperature.
And those extra degrees, emphasizes the specialist, provide us with multiple benefits. From "hindering the multiplication of viruses and bacteria, to making white blood cells function more effectively, in addition to promoting the production of antibodies and accelerating tissue repair."
It is a valuable 'weapon' for our defense system, not a harmful reaction. Therefore, "it is not necessary to treat the fever or try to lower it by all means to the usual temperature," notes Gonzalo de la Fuente, pediatrician and editor of EnFamilia, the website for parents of the Spanish Pediatric Association.
"Current scientific evidence suggests that it is not necessary to treat the fever itself, but the goal is to alleviate discomfort," agrees Asensio López, family physician and coordinator of the Preventive Activities and Health Promotion Program of the Spanish Society of Family and Community Medicine (semFYC), who clarifies that "the current recommendation is to 'treat the patient, not the thermometer'. If the patient is comfortable, hydrated, and active, there is no need to administer drugs."
Antipyretic drugs - such as paracetamol or ibuprofen - should therefore be used "only if the fever causes discomfort, pain, or hinders rest," he emphasizes.
Mozota points out that a person is considered to have a low-grade fever if their temperature exceeds 37.5ºC in a measurement taken in the armpit. Fever is considered from 38ºC onwards, he warns.
In general, fever is not by itself an indicator of needing medical help, emphasizes the family physician. A healthy adult can have a fever for several days because in many cases, the condition will respond to a simple cold that can be easily overcome at home. "You should see a doctor if the fever lasts more than 48 to 72 hours without a clear cause, when the temperature is above 39 and 40º and does not decrease with treatment, if there is difficulty breathing, if confusion appears, if there is neck stiffness, if there is a rash that does not disappear when pressed, if there is intense pain, if there are persistent vomiting, or if the person is immunocompromised," he explains.
In the case of children, "the most important thing is the overall condition accompanying the child," explains Marta Illán, pediatrician at the Hospital Clínico San Carlos in Madrid. "You should consult when the child shows persistent lethargy that does not improve with a decrease in temperature, irritability, signs of difficulty breathing, poor coloration, repeated vomiting, intense headaches, appearance of skin rashes, seizures, pain or difficulty bending the neck," the specialist explains. Additionally, it is also necessary to go to the pediatrician "if the child is very young (under 6 months) or if the fever lasts more than 2-3 days".
"In the first 24 hours, it is normal not to present more symptoms than the fever along with discomfort," De la Fuente agrees. In those initial moments, in the case of children, it is important to monitor alarm symptoms, such as "neck stiffness, general discomfort, very noticeable lethargy, and the appearance of spots on the body that do not disappear when pressed or stretched, known as petechiae."
There are several myths about fever that need to be dispelled, note the consulted experts, who debunk some of the most widespread ones:
Myth: The higher the fever, the more serious the illness. "That is not necessarily true," says Mozota. "There are common viral infections that can cause a temperature of 40º, and conversely, there are also very serious illnesses that can occur without fever." Monitoring warning signs "can be much more useful in any febrile condition than just focusing on temperature," De la Fuente agrees.
Myth: High fever causes seizures or neurological damage. "Febrile seizures will only occur in children predisposed to them, their overall prognosis is favorable and they do not leave neurological or developmental sequelae," explains Illán, who emphasizes that "fever itself does not cause complications. These will only occur when the cause of the fever is a serious illness."
Myth: Cold water showers are effective. In reality, "they are counterproductive, as they can cause chills, which increases discomfort and, paradoxically, can raise body temperature," notes Asensio.
Myth: You must always lower the temperature when it rises above 37º. "The goal is to alleviate discomfort, not achieve a completely normal temperature," Mozota clarifies.
Myth: I should consult as soon as possible to detect the cause and start specific treatment. "In many cases, fever is the first symptom of an infection and when it has a short course, it may not be accompanied by other symptoms or physical signs in the examination, which means that we cannot establish the cause in those early moments," Illán explains. "In a high percentage of cases, the disease causing it will be a virus and the treatment will be symptomatic (abundant hydration and antipyretics if there is discomfort or pain)," she adds.