March 2025

Seasonal Allergies

• Sesonal Allergies 101 – Part 1
• Sesonal Allergies 101 – Part 2
• Seasonal Allergies & Gut Health
• Seasonal Allergies & Stress

This is a heady post (as usual with me). Although I tried to cut the topic into small bites to make it easier to digest, seasonal allergies are a complex condition impacted by the immune, digestive, and endocrine systems. 

In the first two posts about the topic, I explained the foundational concepts of seasonal allergies, such as mast cells and IgE. Today, I want to show you how stress can drive seasonal allergies. 

Seasonal Allergies & Stress

For example, it was found that maternal stress during pregnancy significantly increased the risk of allergies in the infants. At the same time, stress was found to worsen the allergic symptoms of people with allergies.

How does stress affect the immune system?

The adaptive immune system is the part of the immune system that is highly trained and develops a memory of specific irritants and pathogens. It is made out of two branches: B cells and T cells. IgE is a type of B cell. There are four types of T cells, but two play a role in balancing the immune system and allergic conditions: Th1 and Th2. Th2 cells promote the production of IgE. More IgE antibodies mean increased chances of allergic reaction.

Lab tests of people with allergic reactions showed high levels of Th2 immune cells in compression to Th1. Also, when people with allergies were treated with immunotherapy, the proportion of Th1/Th2 in their body was much more balanced. 

Chronic stress suppresses the production of Th1 cells and promotes the production of Th2 cells, increasing IgE production and the risk for allergies.

More recent studies explore how psychological stress and mast cells work together to trigger allergies. 

To understand how stress affects the immune system and can lead to reactive mast cells, thus increasing the risk and severity of allergies, you first need to understand the hormonal cascade that shapes the stress response.

The endocrine, stress, cascade

The body initiates the stress response to internal or external threats.

Some internal conditions that can trigger a stress response are:

• Acute or chronic illness (inflammation)
• Nutrient deficiencies
• Hunger – you skipped a meal
• Dehydration
• Sleep disturbances
• Too much or too little movement

External factors that trigger stress are the daily things that stress us, like work, money, and relationships.

The stress response, AKA fight, flight, or freeze response, is initiated in the endocrine and nervous systems. 

The nervous system gets the endocrine stress response going in three stages:

1. The hypothalamus releases CRH (Corticotropin-Releasing Hormone), a hormone that initiates the stress response or the HPA (Hypothalamus, Pituitary Axis).
2. CRH stimulates the pituitary gland to secrete ACTH (Adrenocorticotropic Hormone).
3. ACTH floats in the blood until it reaches the adrenal gland, a small gland on top of your kidneys, where it initiates cortisol release. 

What does that have to do with allergies?

Three hormones play a role in the stress cascade:
CRH (Corticotropin-Releasing Hormone)
ACTH (Adrenocorticotropic Hormone)
Cortisol

Two out of these three hormones play can affect seasonal allergies: CRH and cortisol.

CRH (Corticotropin-Releasing Hormone) & seasonal allergies

CRH can significantly increase the number of mast cells. It can also bind to IgE receptors on the cell membrane of mast cells, which directly leads to histamine release and allergy symptoms.

When the hypothalamus initiates a stress response, elevated CRH means a potential increase in the number of mast cells and higher chances of these mast cells releasing histamine, increasing the risk of allergies and the severity of symptoms.

On the other hand, when mast cells are activated in the body due to an allergic flare, they increase the gut blood barrier permeability and brain blood barrier permeability, which leads the hypothalamus to release CRH.

Stress and allergies can create a vicious cycle. Chronic stress can lead to allergies, but allergies reduce the body’s resilience to stress and can initiate a stress response by themselves.

Cortisol adrenaline and allergies

Cortisol, a steroid hormone released by the adrenal gland after the HPA cascade, has many bodily functions, including modulating the sleep-wake cycle and keeping us alert. 

Pharmaceuticals containing cortisol and adrenaline (epinephrine) are the main medicines used for severe allergic reactions such as asthma and anaphylaxis because they suppress mast cell activation. 

Studies show that people with lower-than-normal cortisol levels had an increase in IgE antibodies. This antibody triggers mast cells to release histamine, leading to seasonal allergy symptoms. 

Cortisol enhances the activity of epinephrine (adrenaline), a hormone and neurotransmitter that plays a crucial role in the stress response.

The amounts of cortisol in the blood change throughout the day. It is high in the morning and starts to decline in the afternoon and toward the evening. However, keeping a balanced cortisol level high enough to suppress mast cell activation but low enough to prevent chronic stress and an imbalance of Th1/Th2 adaptive immune cells is key for keeping your mast cells stable. 

It is no secret that allergy symptoms are stressful and tiring. Therefore, all people with seasonal allergies will benefit from reducing allostasis stress or the bucket of stressors they carry. At the same time, increasing their resilience to stress can help them mitigate the effect of stress on their allergies. 

The first step to regulating your nervous system and increasing your resilience to stress is starting with lifestyle changes.

• Eat nutrient-dense meals and try not to skip meals.
• Hydrate with plenty of water.
• Get 8-9 hours of restorative sleep at night.
• Move your body daily.
• Spend some time with the community and family.
• Find meaning.