Stages of optimal fever

The definition of "optimal" fever:

Everything that used to be called typical fever with its stages can be classified here. These are the fever curves under the control of the regulatory system that ensure the optimal setting and flow of the immune response and energy efficiency. That is, all febrile episodes that are uncomplicated.

  1. The ascent phase
  2. The peak
  3. The beginning of the decrease
  4. Normalization: end of decrease (129)

What physiological changes occur during each phase?

1) In the ascent stage

Heat production increases: muscles become tense, may be accompanied by trembling, shivers, and muscle tremors.

Increased heat retention: small blood vessels in the skin contract, reducing heat release (heat radiation), hands and feet cool, face pale; as sweat secretion decreases, evaporation also decreases.

The end of this phase is usually the most uncomfortable, and may be accompanied by chills, head and muscle pains and malaise.

Don't worry, the fever will soon pass into the next, more bearable stage!

2) During the peak

Heat production and heat dissipation are in balance, as the body has reached its target, optimal, set point temperature.

Heat production is reduced.

Heat dissipation increases: as the temperature of the blood (core temperature) flowing through the thermoregulatory centre is sufficiently elevated, the signalling of the cooling centre expands the skin's vessels (accompanied by flushing), and the skin's temperature elevates again. The skin and limbs of the person become warm.

This stage is well-tolerated by children, they often sleep through it, although they may still have nightmares.


3) In the initial stages of decrease

After the body has maintained body heat for a sufficient amount of time (usually a few hours) to react optimally with the immune system, it begins to "rest" and further reduces heat production.

The heat dissipation will also increase: it will change, the greater part (up to 75 percent) will be evaporation, more precisely sweating. Unlike older children, babies and toddlers don't always sweat.


4) At the end of the decrease, at normalization

The operation of the thermoregulatory centre will increase again.

Heat dissipation decreases.

This creates the new, low balance.

At this point there is nothing left to do.


Refer to the literature by numbers in this document here: References

Version updated: 08th March 2020