A fever signals a temporary rise in the body’s core temperature, indicating that the immune system is actively responding to an infection. An oral temperature of 100°F (37.8°C) or higher is commonly considered a fever. While often uncomfortable, a fever is a natural defense mechanism. The body’s heightened state can sometimes influence brain function, potentially leading to altered perceptions.
The Connection Between Fever and Hallucinations
A high fever can cause hallucinations, which are perceptions of things not actually present. These experiences can involve seeing, hearing, feeling, smelling, or even tasting things that are not real. These fever-induced hallucinations are generally temporary and tend to resolve as the fever subsides.
The body’s response to illness can influence brain activity, contributing to these altered states. Hallucinations during a fever are sometimes referred to as a type of delirium, a temporary state of mental confusion and disorientation that can accompany an infection.
How Fever Affects the Brain
Fever can impact the brain through several mechanisms. When the body fights an infection, it releases inflammatory molecules called cytokines into the bloodstream. These signals can influence the brain, either by activating specific receptors on the blood-brain barrier or by entering areas where this protective barrier is less restrictive. This inflammatory response within the brain, known as neuroinflammation, can disrupt normal neurological processes.
Elevated temperatures can also affect brain chemistry. High body heat can slow enzymatic actions within the brain, potentially leading to imbalances in neurotransmitters, which are chemical messengers. Additionally, fever can cause dehydration due to increased perspiration, contributing to mental confusion and electrolyte disturbances that impair brain function. Disrupted sleep patterns, common during illness, can also contribute to hallucinations.
Who is Susceptible and When to Seek Medical Attention
Certain individuals are more susceptible to experiencing fever-induced hallucinations. Young children are a common group where febrile delirium occurs, often associated with viral infections like influenza. These episodes in children are usually brief and may not require specific medical intervention. Older adults are also more prone to delirium and confusion with fever, especially if they have underlying conditions such as Alzheimer’s disease, other forms of dementia, or infections like urinary tract infections. Individuals with pre-existing neurological conditions or weakened immune systems may also be at increased risk.
When to Seek Medical Attention
It is important to seek medical attention if hallucinations do not resolve as the fever comes down, or if the fever itself persists.
For adults: Medical evaluation is advised for fevers over 103°F (39.4°C) or if accompanied by symptoms such as a severe headache, stiff neck, rash, chest pain, difficulty breathing, persistent vomiting, or significant mental confusion. A fever lasting more than three days also warrants medical attention.
For infants under three months: A rectal temperature of 100.4°F (38°C) or higher requires immediate medical consultation.
For children aged three to six months: A rectal temperature over 102°F (38.9°C) or lower temperatures with marked irritability or sluggishness should prompt a call to a healthcare provider.
For any child: A fever over 104°F (40°C), or if they are listless, confused, repeatedly vomiting, have a severe headache, or experience seizures, should be seen by a doctor.
Signs of serious infections: Such as meningitis or encephalitis (e.g., sudden severe headache, high fever, disorientation, or stiff neck) necessitate immediate medical care.