The connection between the brain and the immune system has often been ambiguous, but recent studies indicate that they maintain continuous interaction. Research shows that the brain actively participates in balancing and controlling immune functions.
Experts have uncovered neurons in the brainstem that are capable of detecting immune signals from the body’s periphery, acting as key regulators of the inflammatory response.
Understanding the immune system
Composed of various components such as barriers, organs, white blood cells, proteins, and chemicals, the immune system serves to protect our bodies from harmful antigens, facilitating recovery from infections and injuries. This system works in tandem with the nervous system, communicating extensively.
“Communication between the brain and the immune system occurs via the autonomic nervous system,” explains Tanja Wright, a naturopathic doctor and co-owner of Vancouver Naturopathic Clinic.
“This system operates continuously without conscious effort. It comprises two branches: one prompts action (fight-or-flight) while the other promotes relaxation (rest-and-digest). The neural pathways release neurotransmitters that determine immune cell behavior, enabling the brain to instruct these cells to increase activity or quiet down.”
When under stress, the brain activates the body’s alarm responses, preparing for action. “[S]tress leads the brain to release cortisol, the stress hormone,” Wright states. However, prolonged stress can diminish immune function, as excessive cortisol suppresses the immune system, hindering the body’s ability to combat infections or recover from injuries.
It’s well established that the brain influences inflammation, which is integral to the immune system’s defense against harm or diseases. “Too much inflammation, however, can lead to complications,” Wright warns. “While the brain plays a role in regulating this response, overwhelming levels of stress or illness can push inflammation beyond safe limits, resulting in damage.”
How does the brain relate to allergies?
The brain is always vigilant, constantly monitoring for foreign substances (allergens) that may pose a health threat.
The body’s response to allergens
In certain instances, the immune system mistakenly generates antibodies to target allergens that are generally harmless. Upon encountering an allergen, these antibodies secrete histamine into the bloodstream, resulting in symptoms such as inflammation of the skin, sinuses, respiratory tract, or digestive organs.
An overview of allergies
Allergic reactions can manifest for the first time at any age and may be influenced by factors such as hormonal changes, stress, smoke exposure, medications, fragrances, or environmental irritants. Some allergies, particularly those related to specific foods, may resolve over time. Airborne allergens can be seasonal, emerging during pollination, or persistent throughout the year, such as dust mites and pet dander.
Role of the brain in allergic reactions
“The brain significantly influences allergic responses by instructing the immune system on how to react,” Wright explains. In times of stress, sickness, or fluctuating hormone levels, the immune system can be compromised, intensifying allergic reactions.
With repeated exposure to allergens, the brain’s inflammatory response to these substances can become chronic, leading to lasting effects in areas such as the airways, skin, and eyes. “Although the brain helps regulate inflammation, it may struggle to manage it effectively when faced with excessive inflammation from multiple allergies or other pressures, such as stress or illness,” Wright adds.
The link between brain health and allergies
Unhealthy lifestyle choices can negatively impact brain health, which may result in increased sensitivity to allergens and heightened allergic responses. Wright highlights factors like inadequate sleep, poor nutrition, persistent stress, and lack of physical activity, all of which can enhance immune reactivity.
According to Alex Chan, a naturopathic doctor at Integrative Naturopathic Medical Centre in Vancouver, habits such as obtaining seven hours of quality sleep each night can benefit both brain and immune health.
Chan also recommends other practices for nurturing brain health and, consequently, immune function:
- Engage in regular exercise to enhance blood flow and oxygen levels, which also helps reinforce connections in memory-related brain cells.
- Limit alcohol consumption, smoking, and exposure to harmful chemicals that can disrupt neurotransmitter function and damage brain cells.
- Keep the brain engaged as you age by learning new skills, staying socially active, and fostering new neural connections.
- Be mindful of how common conditions like hypertension, diabetes, and chronic inflammation can affect brain health.
- Maintain a balanced diet rich in antioxidants, healthy fats, and proper hydration, while avoiding excessive neurostimulants like caffeine and harmful additives like MSG.
This article first appeared in the April 2025 edition of Intomodel magazine.
