Just before you run to the hospital: Many parents are very familiar with the nighttime scenario. During the day the child feels not too bad at all, and then, toward night, the fever jumps, the child wakes up crying or looks exhausted, and anxiety at home rises. We see this every evening. Parents arrive alarmed because the fever spiked at night, but from a physiological standpoint, this is actually quite expected.
There are three mechanisms that explain why fever rises in the late afternoon/evening hours:
1. The biological clock: The body’s baseline temperature is higher toward evening. This happens in adults too, but in children the difference is more noticeable. Since the biological clock is more active at these hours, the body involves inflammatory mediators that raise the temperature. If we add a febrile illness or febrile seizures, this will be expressed more strongly during these hours, with the peak in the 16:00–20:00 time range.
2. Increased immune activity: At night the body releases substances (cytokines) that activate the immune system. This is a completely natural response. Fever is not an enemy; it is part of the defense.
3. Sleep conditions: Blankets, a closed room, fragmented sleep – all of these increase the body’s difficulty in cooling down.
So when do you really need to worry?
It is important to emphasize that the number on the thermometer is not the main measure: The fever itself worries us less. What matters is how the child looks. Is he responsive? Drinking? Remaining alert? These are the parameters that truly determine the situation. When the child appears to be in pain, breathing rapidly and panting, and has a high fever, the first step is to give a pain reliever and fever reducer.
The fever does not have to disappear, but it should show a downward trend. For example, if we measured a child’s fever at 40 degrees and after giving medication it remains at 38.5, that is good enough.
There are several cases in which you should go to the ER:
- Changes in level of consciousness: Drowsiness even when the fever goes down, or extreme restlessness that cannot be calmed in any way
- Breathing difficulties: Even after the fever drops, the baby/child is still breathing fast and making an effort to breathe
- Very pale or bluish body color
- Frequent and repeated vomiting
- A rash that does not fade when pressed
- High fever accompanied by a poor general condition over time
It is important to know that the body raises its temperature through shivering. The shaking produces energy, and that is what raises body temperature. Unlike a seizure, when you hold the child’s hand, the shivering should pass.
What should be done at home? The golden tips of the ER director:
1. Reducing layers: Many parents cover the child too much. דווקא one should ventilate and allow the child to release heat.
2. Plenty of fluids: Children can become dehydrated quickly. This is one of the most important things to monitor. If it is hard for the child to drink, offer small amounts of fluids more frequently.
3. Medication when needed: Not because of the number, but if the child is not sleeping, is irritable, or in pain. The medication is intended for how the child feels, not for the thermometer.
And what about the tendency to run to the ER at night? It is natural. But many times the situation seems more dramatic because it is night, because everyone is tired, and because the fever reaches its peak. It is important to remember that this is part of a normal immune response.
A rise in fever at night is a natural phenomenon, but it is always best to look at the child, not only at the number.
Dr. Ron Bernat is the director of the ER (Emergency Medicine Department) at Schneider Children’s Medical Center, Clalit Group.