Why Fall Feels Like Flu Season: The Hidden Role of Histamine and Mold

Many people start feeling the “flu season” vibe in fall - heavy head, congestion, watery eyes, fatigue, headaches. I definitely hear this a lot from my clients, but those who do also all had mold exposure or are still living in it. For me, this fall has been a particularly intense reminder of how our environment can influence how we feel.

In the past few weeks, I’ve been dealing with constant teary eyes and a stuffy nose - to the point where I actually took antihistamines in small doses to be able to breathe. While I’ve known for years that I’m sensitive to histamine, this is the first time I’ve really felt how much that sensitivity can flare during the fall.

After mold exposure in the past, my system is still reactive, and my slow HNMT gene (which affects how efficiently the body breaks down histamine) has really shown its impact this year.

The combination of lingering histamine sensitivity and increased mold spores in the air created the perfect setup for allergy-like symptoms that can easily be mistaken for a cold or flu. And in the beginning I even thought that I had caught something. I was dragging it on without really getting better but also not worse - and thanks to my clients, I understood that I too had a histamine problem. 

Why Fall Can Feel Like Flu Season - Even When It’s Not

Fall brings with it a set of environmental changes that make the body work harder to stay balanced:

• More time indoors, often with less ventilation, means greater exposure to indoor dust and mold.

• Damp weather and decaying leaves create ideal conditions for mold growth outside.

• Dry indoor air which dries out your nasal passages and makes it easier for allergens and microbes to irritate your airways.

• Light deprivation and circadian disruption: As the days shorten and we switch from summer to winter time, the body’s internal clock - or circadian rhythm - shifts. Less sunlight affects melatonin, vitamin D, and cortisol balance, all of which play powerful roles behind the scenes in immune resilience and inflammation control. When your rhythm is off, your immune system can become less adaptive and more reactive.

Together, these shifts can make you feel run-down - not necessarily because you’re fighting a virus, but because your immune and histamine systems are under extra pressure.

If you’re ready to uncover what’s really driving your reactions - and learn how to support your body without relying on antihistamines - let’s talk. Request to book a free 30-minute clarity call

The Histamine-Mold Connection

Histamine is a natural chemical that your body uses in immune defense, digestion, and communication between cells. But when your body can’t break it down efficiently - due to genetics, hormone fluctuations, (gut) inflammation, or environmental triggers - histamine builds up, causing symptoms like nasal congestion, headaches, watery eyes, and fatigue. Also acid reflux is a common histamine reaction. 

Histamine isn’t all bad though -  it’s a vital messenger. The trouble begins when your ‘histamine bucket’ overflows and your body can’t clear the excess efficiently anymore.

Mold exposure is one of the lesser-known triggers that can amplify histamine responses. When mold spores are inhaled, they irritate the immune system and stimulate histamine release. For someone who already struggles with slow histamine breakdown (for example, due to HNMT or DAO gene variations), the system can quickly become overloaded.

That’s what I’ve noticed this season - even though my environment hasn’t changed, my resilience has. And because my histamine pathways are still sensitive after previous mold exposure, my tolerance threshold is simply lower.

How Gut Health Influences Histamine Sensitivity

Your gut plays a central role in how well your body manages histamine. Certain bacteria actually produce histamine - including common bacteria found in the gut or even in some probiotics. This means that your ‘healthy’ supplement might be adding fuel to the fire if it contains strains like Lactobacillus casei or fermentum.

And when those strains overgrow, they can raise histamine levels systemically.

One of my current clients who’s battling with severe digestive problems, had exactly this problem which was revealed from the stool test we’ve done together. Her results showed a particularly high number of histamine-producing bacteria. I’ve also noticed this on my own skin that the inflammation caused by high histamine will exacerbate skin conditions like rosacea. I had another client in the past who had a high amount of histamine producing bacteria and I asked him if he ever had itchy skin or rashes and he confirmed that he had actually noticed to have very red and itchy skin when he got into the shower after working out - something he would’ve never mentioned to me hadn’t I asked…

This connection is often missed - but supporting your gut health (by reducing inflammation, balancing the microbiome, and supporting digestive enzymes) can be a game changer for histamine management.

Histamine and Sweat

Interestingly, your body also produces histamine when you sweat - whether during exercise or a sauna session. For some people with histamine intolerance, this can temporarily worsen symptoms like flushing or itching.

That doesn’t mean you should avoid sweating altogether - in fact, sweating also helps your body release toxins and supports detox pathways that ultimately improve histamine tolerance. The key is awareness and pacing: gentle movement and shorter sauna sessions can provide the benefits without overwhelming your system.

Why Histamine Sensitivity Can Worsen in Perimenopause (and With Age)

Many women start noticing more histamine-related symptoms - such as congestion, headaches, itchy skin or skin breakouts, acid reflux, and poor sleep - as they approach their 40s and 50s. Hormones play a big role here.

Estrogen naturally stimulates the release of histamine, while progesterone helps to keep it in check. During perimenopause, estrogen levels fluctuate and progesterone often declines, which can lead to higher histamine activity. This is why symptoms like allergies, anxiety, or food reactions can become more pronounced around midlife.

On top of that, as we age, genetic variations that influence how we break down histamine like DAO and HNMT can become more pronounced. These genes might have been quiet for decades, but under the pressure of declining hormones, accumulated toxins, gut imbalances, or stress, they ‘switch on.’ Suddenly, what you once tolerated just fine - red wine, aged cheese, or even a good workout - can send your histamine bucket spilling over.

Why Reaching for Antihistamines Isn’t Always the Best Long-Term Solution

When symptoms flare, it’s completely understandable to reach for antihistamines - I did the same this season. They can bring temporary relief, but they don’t address why your body is producing or struggling to clear histamine in the first place.

Over time, frequent use of histamine blockers can:

• Disrupt the natural balance of gut microbes, which can worsen histamine issues long-term.

• Interfere with stomach acid and digestion, leading to nutrient deficiencies (especially B vitamins, iron, and zinc).

• Create a kind of “rebound” effect where your body produces more histamine once you stop the medication.

Histamine blockers may bring short-term relief, but they’re a bit like putting tape over a warning light on your car dashboard. The signal stops showing, but the underlying issue keeps brewing. 

Instead of simply blocking histamine, supporting your body’s ability to metabolize and clear it can make a lasting difference.

Supporting your natural histamine breakdown - through DAO or HNMT support, balancing gut microbes, managing stress, and reducing estrogen dominance - addresses the root cause!

Depending on your genetic profile and main pathway (DAO vs. HNMT), this might include:

• DAO enzyme support (if the issue is in gut breakdown)

• Methylation support (for HNMT sluggishness)

• Herbal antihistamines (nettles, quercetin, and curcumin)

• Mast cell stabilizers (vitamin C, magnesium, phosphatidylcholine, polyphenols)

• Gut rebalance and liver detox support

These approaches help your body restore balance instead of suppressing a system that’s actually trying to communicate distress.

Supporting Your Body During Fall’s “Flu-Like” Season

If you’re also noticing allergy-type symptoms this time of year - sinus congestion, itchy eyes, or that constant “almost sick” feeling - here are a few strategies that can help support your body naturally:

1. Reduce Mold Exposure

   • Keep windows closed on damp, windy days

   • Use a HEPA air purifier indoors

   • Clean humidifiers and heating vents regularly

2. Support Histamine Breakdown

   • Focus on foods that help clear histamine, such as fresh vegetables, herbs like parsley, and vitamin C–rich foods

   • Avoid leftovers and high-histamine foods (like aged cheese, wine, and fermented products) when symptoms flare

   • Consider DAO or herbal support if appropriate.

   • Go gluten & dairy-free (this is not a direct link but helps reduce inflammation overall)

3. Align with Light and Circadian Rhythm

4. Get natural daylight exposure early in the day.

5. Dim lights in the evening and maintain regular sleep patterns.

6. Support Detox & Stress Regulation

   • Stay hydrated and include fiber to help bind and eliminate toxins.

   • Practice calming routines — histamine and stress hormones like cortisol influence each other.

7. Rest and Manage Stress

   • Histamine and stress are closely linked; when cortisol rises, histamine can too.

   • Deep breathing, gentle movement, and rest all help regulate both systems.

If you suspect histamine overload or mold exposure might be behind your “mystery symptoms,” you don’t have to navigate it alone.

If you’re ready to uncover what’s really driving your reactions - and learn how to support your body without relying on antihistamines - let’s talk.

Request to book a free 30-minute clarity call