Sneezing? Itchy, watery eyes? Read this.

Good morning!

Spring is here, plants are releasing pollen, and your immune system is having none of it. As promised, this week we’re talking about pollen, allergies, why your body reacts, and most useful to you, what you can do about it.

Key Takeaways

• Pollen allergies are driven by an immune response originally meant to fight parasites, but it can misfire, treating pollen as a threat.

• Early immune system “training” matters, limited microbial exposure in childhood is linked to higher allergy risk, but it is not the only factor.

• Genetics set your baseline risk, while environment and exposure determine if and when allergies actually show up.

CORE

The Defense System That Misfired

Pollen is, practically speaking, harmless. It's not a virus, not a bacteria, not a toxin. In essence, your immune system is attacking something that poses no threat to you. But, why?

A specific part of your immune system runs the allergy response, and at the center of it is an antibody called IgE. When IgE attaches to immune cells in your airways, skin, and gut, those cells become primed. The moment they detect something they’ve learned to flag as a threat, they release inflammatory chemicals like histamine.

That system wasn’t designed for pollen, but for parasites. That’s right, parasites.

Without getting too gross, for most of human history, parasitic worms were everywhere. As a biological response, your immune system had to get very good at spotting them quickly and forcing them out.

IgE is part of that strategy. When a parasite enters through the skin or gut, IgE recognizes proteins on its surface and triggers a response: inflammation, mucus, muscle contractions. Not pleasant, but effective. The goal is simple: make the environment hostile enough that the parasite can’t stay.

And it works. But here’s where things don’t go as intended. Some of the proteins found in parasites look incredibly similar like proteins found in completely harmless things, such as pollen, dust mites, even certain foods. Your immune system doesn’t really know the difference. It’s reacting to patterns it learned to associate with danger.

The Hygiene Hypothesis

Ok, so we have a misfiring defense system. Now the question becomes, are we doing something that causes this misfire to happen more often?

Allergies have become dramatically more common over the past century, particularly in industrialized countries. In 1989, epidemiologist David Strachan observed that children from larger families had significantly lower rates of hay fever and eczema than children from smaller families. He proposed that infections transmitted through contact with siblings during early childhood were somehow protective against allergies.

This became known as the hygiene hypothesis. The idea that reduced exposure to microbes and infectious agents in early childhood prevents the immune system from developing properly, making it more likely to overreact to harmless substances.

The evidence supporting this has accumulated. Children raised on farms have substantially lower rates of allergies and asthma than children raised in urban environments. Early daycare attendance (more microbial exposure from other children) correlates with reduced allergy risk. Children with older siblings have lower allergy rates than firstborn children.

The mechanism appears to be immune system education. During early childhood, your immune system is learning what's dangerous and what isn't. Exposure to diverse microorganisms, bacteria, viruses, and yes, parasites, trains your immune system to distinguish between actual threats and harmless environmental proteins.

Without enough early exposure, the immune system never fully learns what’s harmless and what’s not. So later on, it’s more likely to overreact, treating something like pollen as a threat.

Genetics and Late-Onset Allergies

Before anyone who grew up rolling in mud or constantly exposed to microbes sends me a strongly worded letter, yes, genetics plays a major role here.

It’s not all determined by where or how you were raised. Actually, it’s largely genetics. Early-life microbial exposure influences how your immune system is calibrated, but it doesn’t fully decide whether allergies will develop. Studies show that if both your parents have allergies, your risk is around 50-80% of having to endure the same. One parent brings it down to 30-50%, and even with none, there’s still about a 12% chance. What you inherit isn’t a specific allergy, it’s a tendency to overreact.

Whether that tendency shows up heavily depends on your environment. That’s why allergies can appear at any age. The immune system is built to prevent overreacting, so it constantly regulates itself to avoid reacting to harmless triggers. Allergies happen when that balance shifts, either the control is less effective or the trigger response becomes strong enough that the system can no longer hold it back.

What You Can Do

If you’re dealing with spring allergies, the most effective first step is reducing exposure. Keep windows closed on high pollen days, and shower before bed to remove pollen from your hair and skin so you’re not carrying it into sleep. Indoors, an air purifier with a HEPA filter (a high-efficiency filter that traps very fine particles like pollen, dust, and pet dander) can significantly reduce what’s circulating in the air.

When you do need to be outside, the goal is minimizing how much pollen gets on you and preventing what does from staying there. Protecting exposed areas like your eyes and face is your best bet.

Regular moderate exercise, done indoors during pollen season, can also help reduce allergy symptoms by decreasing inflammatory markers and improving blood flow, which helps clear allergens from your body more quickly. Studies show activities like cycling, brisk walking, and resistance training reduce nasal symptoms and inflammation.

Another potential option is over-the-counter antihistamines, which can help block symptoms like sneezing and itching. If symptoms are interfering with daily life, and you’re looking for a long-term solution, an allergist can help identify your specific triggers so you can focus your avoidance and treatment more precisely.

ENDNOTE

Final Thoughts

Questions? Ideas for a newsletter topic? Feel free to chat by replying to this email!

Hungry for more allergy-related reads? Check out this edition, where I break down food allergies in depth.

Until next week!

Adrian Macdonald | Team Dietitian | The 8% Newsletter Author