Fever: understand the causes and know how to lower the temperature

Fever is a sign that the immune system is at work.

Despite being a state of alertness, it is not always serious and can even be a good sign: the body is dealing with inflammation or infection.

Fever above 37.8ºC is considered fever, and the normal temperature is up to 37.2ºC. In cases of doubt, it is always necessary to seek medical advice and never resort to self – medication .


What is fever?

Fever, or pyrexia, is not characterized as a disease, but rather as a symptom, as it is a phenomenon of natural defense of the organism and that fights alterations, such as infections.

Its function is to improve the response time of cells, eliminating invaders, such as viruses and bacteria, and it occurs by increasing the body temperature. It is very common and can reach anyone, of any age group.

However, the most affected public are children, as they are in the development phase, practically all viruses and bacteria are unknown to your body.

This symptom also stimulates the proliferation of lymphocytes, increases the activity of macrophages, reduces the effect of some thermosensitive endotoxins and reduces the activity of pathogens, which grow better at room temperatures.

When the body is feverish, the hypothalamus, the area of ​​the brain that controls body temperature, raises the body temperature above normal.

Because it is a natural defense mechanism, it is not always necessary to treat it with medication, as it will expel the foreign body and gradually decrease. Most of the time, the invaders are eliminated even before the disease spreads.

For health professionals, above 37.8 ºC it is already considered a fever. Temperatures below that, but above 37.2 ºC are classified as feverish.

Temperatures above 40ºC, classified as high level, can be dangerous and require treatment at home and medical attention. They can also cause delusions and convulsions , especially in children and the elderly.

Body temperature can also rise for other reasons, such as:

  • In the second part of the woman’s menstrual cycle;
  • During the practice of physical activities;
  • Strong emotions;
  • Warm clothes;
  • Side effect of some medication;
  • High ambient temperature;
  • High humidity.

Types of fever and feverish state

Fever is classified into three different temperature levels:

  • Low intensity fever , when the temperature is between 37.8 ºC and 38 ºC;
  • Fever of moderate intensity , when the temperature is between 38 ºC and 39 ºC;
  • High intensity fever , when the temperature is above 39 ºC.

In cases of high-intensity fever, with temperatures above 40 ºC, there can be significant damage to neurons.

There is also apyrexia, or absence of fever, and the identification of its temperatures are:

  • Axillary temperature : between 35.5 ºC and 36.5 ºC;
  • Oral temperature : between 36 ºC and 37.4 ºC;
  • Rectal temperature : between 36 ºC and 37.8 ºC.

The rectal temperature is usually 0.5 ºC above the axillary temperature, if it is 1 ºC above it may indicate a low abdominal or pelvic inflammatory process.

Causes of fever

Fever can have several causes, and the body’s reaction is quite common. Among the most recurring are:


Because it is caused by a foreign body that enters the body, fever can be caused by several items, such as:

  • Virus;
  • Insolation;
  • Sunburn;
  • Some medications and drugs, such as antibiotics;
  • Adverse reaction to any vaccine;
  • Dehydration.


Fever is also commonly caused by diseases, such as:

  • Infectious diseases such as viruses, bacterial infection and systemic ringworm;
  • Inflammatory diseases such as arthritis, meningitis and inflammatory bowel diseases;
  • Immunological diseases such as rheumatoid arthritis, granulomatosis with polyangiitis, autoimmune hepatitis and lupus erythematosus;
  • Coagulation disorders such as thrombosis;
  • Metabolic diseases such as gout, porphyria and Fabry’s disease;
  • Destruction of tissues such as hemolysis, crushing, infarction and stroke;
  • Malignant tumors like neoplasms.


During a postoperative period, it is common for the body temperature to rise to 37.8 ºC, but temperatures above 38 ºC may reflect some diseases, according to the time elapsed since the surgery:

  • Up to 48 hours after : atelectasis (lung problems);
  • Third or fourth day after : pneumonia;
  • Fifth day after : purulent accumulation in the surgical area.

Fever Symptoms

Because it is a symptom resulting from foreign bodies that are allocated in the body, fever can react differently in adults and children, since each organism has a different development from the other.


The most common symptoms of fever are:

  • Sweat;
  • Shaking;
  • Headache;
  • Muscle and joint pain;
  • Dehydration;
  • Weakness;
  • Apathy;
  • Irritability;
  • Indisposition;
  • Loss of appetite;
  • Dry mouth;
  • Palpitations;
  • Dizziness.

Children and babies

In children and babies, the fever sets in from 37.3 ºC and can have some symptoms different from adults, such as:

  • Lack of sleep;
  • Lack of interest in games;
  • Lethargy;
  • Diarrhea;
  • Vomiting;
  • Earache;
  • Cough;
  • Sore throat.

When the temperature is very high, the child may hallucinate and even convulse.

Are chills and body pain symptoms of fever?

No, because fever, in itself, is a symptom. However, many infections, inflammations or illnesses that cause fever can also cause body aches and chills. Therefore, it is always necessary to investigate the causes of fever, eliminating the origin of the alteration.


Commonly, to confirm the diagnosis of fever, one must take the body temperature and, for that, there are several types of thermometer: the oral, rectal, ear and forehead.

The most common use is that of the oral thermometer, which can also be used in the armpits. You should place the thermometer in your armpit, cross your arms over your chest and wait between four and five minutes.

The use of the rectal thermometer is common in children and is used by placing a little petroleum jelly on the thermometer and carefully inserting it, with the child lying on its belly, from 1/2 to 1 inch in the rectum. Hold the child for three minutes until the temperature is measured.

When the doctor should be contacted

See a general practitioner or pediatrician if your symptoms fall into any of these topics.

In children

  • When the child is apathetic, irritable, vomiting suddenly, he has severe headache or stomach pain, or any other symptom that causes great discomfort;
  • When you have a fever after being left in a hot car;
  • When the fever lasts more than three days;
  • Children under 3 months with a temperature of 38 ºC or higher;
  • Between 3 and 24 months and has a temperature up to 38.9 ºC;
  • Newborn with a lower temperature than usual, below 36 ºC.

In adults

  • When the temperature is 39.4 ºC or higher;
  • When the fever persists for more than three days.
  • If the fever is accompanied by any of these symptoms:
  1. Strong headaches;
  2. Swelling in the throat;
  3. Uncommon rash;
  4. Unusual sensitivity to light;
  5. Torticollis;
  6. Mental confusion;
  7. Persistent vomiting;
  8. Difficulty breathing or chest pain;
  9. Apathy or irritability;
  10. Abdominal pain or when urinating;
  11. Muscle weakness or sensory changes;
  12. Any other unexplained symptom.

Treatment: which medicine to lower the fever?

In general, if the fever does not cause discomfort there is no need to treat it. Because it is a symptom, treatment is directly linked to the disease that manifested itself. In that case, treatment must follow medical guidelines.

However, to relieve the symptoms of fever in a natural way, the patient can remain at rest, take lukewarm baths, stay hydrated and cool the environment.

If natural forms are not effective, there are antipyretic or antipyretic drugs that can be used to reduce the discomfort of fever:

  • Tylenol , Ibuprofen, Dipyrone and Naproxen are the most common medicines to treat fever.

Doses for children under 6 months should be prescribed by the pediatrician.

Children under 28 days of age, on the other hand, should be taken to the hospital for tests and treatments, since at that age a fever may indicate some serious infection, which may require intravenous medication and 24-hour monitoring.

The aspirin should not be used to reduce fever in children or adolescents, because when taken during viral diseases can be linked to Reye’s syndrome, a disease that causes prolonged vomiting, confusion and even coma.

Very high doses of paracetamol can also damage the kidneys and liver. The aspirin should not be taken in cases of dengue fever and some viral infections common in children.


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained on this site is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Tips: home remedy to lower the fever

Fever is a very common symptom in most illnesses, so it is very common to have to deal with it. To make you feel more comfortable during this period, there are a few things the patient can do:

  • Make cold compresses on the trunk and limbs : use a towel or a thermal bag to help lower body temperature;
  • Resting : resting helps to avoid overloading the body, in addition to being more comfortable due to body aches and pains;
  • Take a warm bath : the warm water temperature can help the patient to return to their ideal body temperature;
  • Use cotton fabrics : cotton helps to ventilate better and reduce the sensation of discomfort, especially in times when intense sweating occurs;
  • Staying hydrated : drinking lots of fluids helps to lower your body temperature and prevents dehydration;
  • Eat properly : eating light, easily digestible things can be instrumental in keeping the patient healthy.

Complications: what can high fever cause?

If the patient does not take care of himself or the fever is at a high level, there may be some complications, such as:

  • Severe dehydration;
  • Hallucinations;
  • Fever-induced seizure.

What is febrile seizure?

Febrile seizures are induced by very high body temperature and occur more easily in children between 6 months and 6 years. It is sudden, it can last a maximum of 2 minutes and, although frightening for parents, it does not usually leave any sequels.

In the event of a febrile seizure, your child may become pale, with stiff muscles or making some strange movements, and may even lose consciousness. There are a few things that can be done:

  • Place your child on his side or face down;
  • Remove objects that might hurt you up close;
  • Loosen tight clothing;
  • Hold the head to avoid injury or choking;
  • Do not leave or put anything in your child’s mouth;
  • Time the duration of the seizure.

If the seizure lasts more than 4 minutes, take the child to an emergency room. After the episode, if the child is acting normally, there is no need to take him to the hospital.


It is possible to prevent fever by reducing exposure to infectious diseases. These tips can help you in this regard:

  • Always wash your hands and teach your children to do the same, especially before eating meals, after using the bathroom, after coming in contact with a crowd or someone who is sick, after coming in contact with animals and during and after traveling on public transport;
  • Teach your children how to wash their hands properly by soaping both sides of the hand;
  • Carrying disinfectant wipes in the bag ;
  • Avoid touching your nose, mouth and eyes , they are the main means by which viruses and bacteria penetrate the body;
  • Cover your mouth and nose when you cough or sneeze ;
  • Avoid sharing glasses, water bottles and other utensils that come in contact with mucous membranes.


Always contact a doctor for further guidance and to diagnose the cause of the fever.

Common questions

What to do to lower fever that does not pass with medicine?

Fever is a response from the body. Often, the use of medications without medical guidance ends up interfering with the action of immunity, causing the symptoms to be camouflaged.

Therefore, the ideal is always to investigate the causes and only use prescription drugs. Any fever that does not pass or goes down, especially with the use of antipyretics, needs to be investigated.

What to do to lower fever from 39 degrees?

High fever, above 39 ºC, should always be evaluated by doctors. The condition may be related to more severe infections or inflammations, especially if there are other associated symptoms, such as vomiting, nausea, chills and fainting.

Therefore, treatment should always be based on the diagnosis, otherwise, it may be that there is a worsening of the condition. That is, nothing should be used to lower high fever without medical advice.

Dipyrone lowers the fever in how long?

According to the package insert, dipyrone begins to take effect between 30 and 60 minutes after administration. Its effect lasts for about 4 hours. Therefore, the drop in temperature should start to occur in about 1 hour after taking the medicine.

Remembering that the action can be gradual, taking some more time to reach the appropriate body temperature.

Is there an antibiotic for fever?

The antibiotics are used to treat bacterial infections, not directly fever. Therefore, the temperature is regulated by combating the infectious agent. It should not be used without medical advice or as a treatment for isolated fever.