Fever in babyê: how many degrees, causes and what to do

A baby's body temperature rise should only be considered a fever when it exceeds 37.5°C in an armpit measurement, or 38.2°C in the rectum. Before this temperature, it is only considered to be just a fever, which is generally not a cause for concern.

Whenever the baby has a fever, check for other symptoms because, normally, teething and taking a vaccine can generate a fever of up to 38ºC, but the baby continues to eat and sleep well. In this case, placing a washcloth soaked in cold water on the baby's forehead can help bring the fever down.

Although a baby's fever is considered to be from 37.5°C in the armpit or 38.2°C in the rectum, it is usually only likely to cause brain damage when it exceeds 41.5°C or higher.

What can cause a baby fever

The rise in body temperature indicates that the baby's body is fighting some invading agent. The most common situations that cause fever in babies are:

• Birth of teeth: It usually happens from the 4th month onwards and you can see the swollen gums and the baby always wants to have his hand in his mouth, in addition to drooling a lot.
• Reaction after taking a vaccine: It appears a few hours after taking the vaccine, and it is easy to relate that the fever is probably a reaction
• If fever develops after a cold or flu, sinusitis or ear inflammation may be suspected: The baby may not have phlegm or appear to have a cold, but the internal tissues of the nose and throat may be inflamed, causing fever.
• Pneumonia: Flu symptoms become more intense and fever appears, making it harder for the baby to breathe;
• Urinary tract infection: Low-grade fever (up to 38.5°C measured at the anus) may be the only sign in children under 2 years of age, but vomiting and diarrhea may occur, abdominal pain and loss of appetite.
• Dengue: more common in summer, especially in epidemic areas, there is fever and loss of appetite, the child is sluggish and likes to sleep a lot.
• Chickenpox: There is fever and itchy skin blisters, loss of appetite, and abdominal pain may also appear.
• Measles: Fever lasts 3 to 5 days, and there are usually signs of cough, runny nose, and conjunctivitis, as well as dark patches of skin.
• Scarlet fever: There is fever and sore throat, the tongue is swollen and like a raspberry, small spots appear on the skin that can cause peeling.
• Erysipelas: There is fever, chills, pain at the affected site that may become red and swollen.

When suspecting that the baby has a fever, measure the fever with a thermometer, and observe if there are other signs or symptoms that can help identify what is causing the fever, but in case of doubt, going to the pediatrician, especially when the baby is less than 3 months old.

How to measure a baby's fever

To measure the baby's fever, place the metal tip of the glass thermometer under the baby's arm, leave it there for at least 3 minutes, and then check the temperature on the thermometer itself. Another possibility is to use a digital thermometer, which shows the temperature in less than 1 minute.

Temperature can even be measured more accurately in the baby's rectum. However, in these cases, it is important to take into account the rectal temperature is higher than the buccal and axillary temperature, so when checking the temperature, you should always check the same place, the most common being the armpit. The rectal temperature can be between 0.8 and 1ºC higher than the axillary one, so when the baby has a fever of 37.8ºC in the armpit, he probably has a temperature of 38.8ºC in the anus.

To measure the temperature in the rectum, it is mandatory to use a thermometer with a soft and flexible bridge that must be introduced at least 3 cm

See more about using the thermometer correctly.

Tips to lower baby fever

What to do to lower the baby's fever is:

• Check if the environment is too hot and if possible turn on a fan or air conditioning;
• Change the baby's clothes for a lighter and cooler one;
• Offer something liquid and cool for the baby to drink every half hour, if he is awake;
• Give the baby a bath, from lukewarm to cold, avoiding very cold water. The water temperature should be closer to 36ºC, which is normal skin temperature.
• Placing a washcloth soaked in lukewarm to cold water on your baby's forehead can also help reduce fever.

If the fever does not go down within half an hour, consult the doctor, especially if the baby is very irritable, cries a lot or is apathetic. The medicine indicated to reduce fever in the baby is Dipyrone, but it should only be used with the pediatrician's knowledge.

Check out other options to lower your baby's fever.

How to know if a fever is severe

Fever is always severe when it reaches 38ºC, deserving all the attention of parents and a visit to the pediatrician, especially when:

• It is not possible to identify that the teeth are erupting and that there is probably another cause;
• There is diarrhea, vomiting and the child does not want to breastfeed or feed;
• The child has sunken eyes, is more weepy than usual, and does not pee very little, because it may indicate dehydration;
• Spots appear on the skin, itching or if the baby seems very uncomfortable.

But if the baby is just limp and sleepy, but with a fever, you should also go to the pediatrician to find out what is causing this increase in temperature and start the appropriate treatment with medication.