Why City Air Triggers Allergy Symptoms: Mast Cell Activation Symptoms, Pollution & Perimenopause

When Cold Air Isn’t the Real Problem

Christmas week, I went for what should have been a simple winter walk. The air was cold, but nothing extreme. Within minutes, my eyes were streaming with tears, my nose started running, and by the time I was back home, my eyes were visibly swollen. Not just for an hour - but for the rest of the day.

At first glance, this sounds like a normal cold-weather reaction. But here’s the part that made me stop and really question what was going on:

Just a couple of days before, I had gone for a walk in much colder weather in my hometown in Germany. I was staying in a house with plenty of dust, visible cat hair, and no particularly strict cleaning routine. In theory, a perfect storm of allergens.

And yet… no swollen eyes. No lingering reactions.

Back in Brussels, however, the symptoms returned - and not just for me. A client had recently shared that she always needed antihistamines when living in Brussels, but never when she was traveling.

That’s when a pattern became impossible to ignore.

You know that I love to get to the root of these kinds of riddles (and I just always have to understand what’s going on in the human body), so I had to dig deeper….

Mast Cell Activation Symptoms: When “Allergies” Aren’t Really Allergies

Many people assume watery eyes, swelling, congestion, or sneezing must be due to seasonal allergies. But for a growing number of women - especially in midlife - the real driver is mast cell activation.

Mast cells are immune cells designed to protect us from danger (in form of foreign invaders). They release substances like histamine when they sense a threat. The problem? They can become overly sensitive and start reacting to things that aren’t truly dangerous.

Common mast-cell triggers include:

• Air pollution

• Diesel exhaust particles

• Cold, dry air

• Mold fragments (not just visible mold)

• Chemical irritants

• Stress and hormonal fluctuations

Unlike classic allergies, mast-cell reactions:

• Can come and go unpredictably

• Are often worse in certain environments (like cities)

• Don’t always show up on standard allergy tests

• Can linger for hours or days after exposure

And very often, the eyes are the first place you see it.

Could This Be Mast Cell Activation? A Quick Checklist of Symptoms:

You may relate to this article if you regularly experience:

• Watery, burning, or itchy eyes when outdoors

• Puffy or swollen eyes that linger for hours or days

• A runny or congested nose without a clear allergy

• Symptoms that worsen in cities but improve on holiday

• Increased sensitivity to cold air, pollution, or chemicals

• Reactions that started or worsened in your 40s

• Allergy-like symptoms with normal allergy tests

If several of these resonate, mast cell activation - rather than classic allergies - may be part of the picture

Why Cities Like Brussels Can Be So Triggering

Urban air contains a complex mix of irritants that are particularly activating for mast cells and cause mast cell activation symptoms:

1. Fine particulate matter (PM2.5 & ultrafine particles)

These particles are small enough to penetrate deep into mucous membranes - including the eyes and sinuses. They directly stimulate mast cells to release histamine.

2. Traffic-related pollution

Diesel exhaust and nitrogen dioxide (NO₂) are powerful inflammatory triggers. Even in winter, when pollen is low, these pollutants remain high. (I often get bothered by passing cars smelling their exhaust which doesn’t seem to clear up - especially in cold air)

3. Cold air as an amplifier

Cold air constricts blood vessels and reduces normal mucous clearance. This allows pollutants to sit longer on delicate tissues, increasing irritation and swelling.

4. Mold fragments don’t disappear in winter

While mold spores may be lower, microscopic mold fragments and mycotoxin-containing particles remain airborne year-round - especially in damp urban environments.

The result? Mast cells around the eyes and nose become overstimulated, leading to:

• Watery or burning eyes

• Swelling or puffiness that lasts all day

• Runny or congested nose

• Facial pressure or heaviness

Why This Hits Women in Perimenopause Harder

Perimenopause adds another critical layer to this picture.

Estrogen plays a key role in mast cell behavior. When estrogen levels fluctuate - as they do dramatically in perimenopause - mast cells become more reactive and release histamine more easily.

This means:

• Symptoms can suddenly appear “out of nowhere” in your 40s

• Reactions may worsen at certain points in your cycle

• Antihistamines may become less effective or needed more often

• You may react to environments you previously tolerated just fine

Add to that:

• Slower detoxification capacity

• Higher inflammatory load

• Increased nervous system sensitivity

• And let’s not forget often low progesterone which is actually helping our body decompose histamine

And the threshold for symptoms becomes much lower.

This Isn’t “Just Allergies” - It’s a Load Issue

One of the most important concepts to understand is total histamine and inflammatory load.

It’s rarely one trigger alone. Symptoms appear when the combined load becomes too much:

• Air pollution

• Cold exposure

• Hormonal fluctuations

• Stress

• Gut or liver overload

That’s why symptoms can be:

• Worse in certain cities

• Better on holiday

• Present one day and gone the next

And why treating only the symptom - with antihistamines - often doesn’t solve the root issue.

What Can Help (Beyond Antihistamines)

While reducing exposure isn’t always possible, small strategies can make a meaningful difference:

• Wearing wraparound glasses or sunglasses outdoors

• Covering the nose and mouth with a scarf in cold, polluted air

• Rinsing eyes with preservative-free saline after being outside

• Supporting mast cell stability nutritionally (when appropriate)

• Addressing gut, liver, and detox pathways

• Supporting hormonal balance in perimenopause

Most importantly, understanding why your body is reacting changes how you approach healing.

If you live in a city and notice that your symptoms improve dramatically when you travel, this is an important signal - not something to dismiss.

For many women, these reactions are an early warning sign that the immune system, hormones, and environment are no longer in balance.

And once you see the pattern, you can finally start addressing the root cause - instead of blaming the cold, the season, or “getting older.”

Supporting Your Body This Spring: Gentle Detox for Sensitive Systems

For women with histamine intolerance or mast cell sensitivity, detoxification needs to be gentle, hormone-aware, and supportive, not aggressive.

This spring, I’ll be running a Seasonal Detox focused specifically on environmental toxins and hormone disruptors -  designed for women over 40 whose bodies are already under inflammatory and hormonal pressure.

This approach supports:

• Liver and gut detox pathways

• Reduction of everyday chemical and pollution exposure

• Cleaning up clogged hormone receptors from environmental toxins

• Hormone balance during perimenopause

• Mast cell and histamine regulation

If your body feels overwhelmed rather than resilient, this kind of targeted detox can make a meaningful difference.

Join the waitlist now - sign up here!

If you’re a woman over 40 dealing with unexplained allergy-like symptoms, histamine issues, or environmental sensitivities, this is a conversation worth having - because your body isn’t malfunctioning. It’s responding.