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Headache and Fever: Why They Happen

Written by Stephanie Nera, RPh, PharmD · Pharmacology

Updated Jun 27, 2021

Headache and Fever: Why They Happen

Imagine waking up one morning with your head pounding and in a pool of your own sweat. If this has happened before, you are not alone. Headache and fever can happen separately, but when they occur together this means double the trouble. Let’s talk about why these two conditions happen together and what it means.

Causes of headache and fever

If someone has ever told you that your illness is “all in your head“, they are technically correct. The exact causes of headaches and fever are not well understood. But from what we know, the brain is the centerpiece in these processes.

Our brain has several centers and pathways that handle all the information about things going on in our body. In particular, the thalamus plays a major role in pain modulation while the hypothalamus is in charge of maintaining our body temperature. There are additional areas that are involved with pain perception. However, these will not be discussed in detail.

The brain receives information from afferent nerves located all throughout the body, in places such as our skin, muscles, and internal organs. On the other hand, efferent nerves carry signals from the brain to these areas, creating responses such as movement, secretion, and chemical release. 

For example, when the body starts overheating afferent signals tell the brain we need to cool down. As a response, the brain sends efferent signals to the sweat glands to produce sweat, thus lowering our body temperature.


Interestingly, the brain itself does not have pain receptors (nociceptors) so it does not feel pain. However, the meninges which cover our brains are highly sensitive to pressure and pain. Because of this, infections that can affect this covering, such as meningitis, cause severe headaches. Changes in blood pressure also have an effect on the blood vessels around the meninges, which can cause pain or discomfort.

Fever (pyrexia)

Normally, our body maintains a core temperature of 36.5–37.5°C (97.7–99.5°F). Pyrogens or fever-inducing substances increase the amount of prostaglandin E2 (PGE2) in the body. When this PGE2 reaches the hypothalamus, it raises the body temperature. The “new” normal setpoint is typically raised to 1 to 2°C higher. Additionally, PGE2 contributes to inflammation and pain in headache and fever occurring together.

During a fever, the brain wants to maintain this higher temperature, so our environment feels colder than usual. This is why we tend to shiver and bundle up even if it’s already summertime and everyone else is trying to stay cool.

When should you be worried about a headache and fever?

headache and fever

Headaches and fevers are common and usually self-limiting when associated with a viral infection, such as a cold or flu. Staying hydrated, taking OTC meds, and resting are generally enough for a few days. However, if you have been taking fever medications for more than 3 days or pain relievers for more than 7 days, then your illness may be serious. If this is the case, now would be the time to seek medical attention from a physician.

Additionally, if you can say your headache is the “worst headache of my life” and hit you quickly, this may be a medical emergency. A thunderclap headache with or without neck stiffness and pain can point to serious conditions such as brain aneurysm, hemorrhage, or stroke.

Interestingly, a fever is one of the body’s natural defense mechanism against infections. Raising the core body temperature aims to kill off pathogens and speed up metabolic processes. In the case of viral infections, fever is generally mild and goes away on its own. However, for bacterial infections, higher fevers may occur and do more damage if unmanaged.

High-grade fever occurs when the body temperature reaches 39.4°C (103°F), while extremely high fever (hyperpyrexia) happens at >41.5°C (>106.7°F). At these temperatures, dehydration, muscle spasms, seizures, and altered mental state can occur. High-grade fevers may point to serious infections such as sepsis or even head trauma.

Key Takeaways

In summary, headache and fever can happen together or separately.

While there are different triggers, the brain is responsible for feeling pain and producing fever. Mild pain and low-grade fevers can be “sweated out” or treated with OTC medications such as paracetamol and ibuprofen.

However, if fever persists for more than 3 days or pain continues for more than 7 days, it is time for a check-up. Extremely painful or high headaches and fevers can be medical emergencies, so seek help right away.

Learn more about Headaches and Migraines here


Hello Health Group does not provide medical advice, diagnosis or treatment.

Written by

Stephanie Nera, RPh, PharmD


Updated Jun 27, 2021

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