What Triggers Sniffles, Sneezes & Congestion

An inside look at how your body works

Every second of every day, tiny but potent cells inside the body are fighting to keep us healthy—most of the time without us even knowing. These cells are part of the immune system, a highly coordinated and efficient team designed to fight off anything that might make us sick.

Many times when we just feel a little under the weather but never actually get sick, that’s our powerful immune army working behind the scenes. Even when we do get sick, developing symptoms like a fever, aches and pains, and a runny nose and/or congestion, that’s also our immune system working to fight off the virus or bacteria that infected us. Needless to say, without our immune system we wouldn’t be able to survive.

Inflammation: How & Why Symptoms Begin

Inflammation is an essential protective tool of the immune system to fight off what it considers to be harmful invaders: that is, anything that can potentially cause injury to the body. In those who suffer from allergies, the immune system sees pollen, mold, and ragweed, to name just a few triggers, as harmful invaders that need to be vanquished. When the immune system senses this invader, it begins to wage war on it.

To aid in this fight, immune cells at the scene of the invasion (e.g., in the nasal passages and/or the lungs) release natural chemicals called cytokines. It’s these chemicals that trigger symptoms of inflammation. In those with sinus or respiratory symptoms, these include swelling and constriction of the airways, excess mucus production in the breathing passages causing a runny nose or nasal congestion, sore throat, headache, and/or just feeling lethargic. (It’s cytokines, by the way, that also trigger fevers, which are an attempt by the body to burn off and kill invaders like viruses and bacteria.)

Inflammatory symptoms are an attempt by the immune system to rid the body of the invader. Sneezing, for example, is meant to force it out of the body, as is coughing. Sticky mucus is designed to attach itself to the invader and pull it out of the body, while swelling is meant to draw more fighting reinforcements (e.g., blood and immune cells) to the area. In these situations, inflammation is a good thing: it’s meant to turn on to help the immune system get rid of an invader and turn off when the invader has been beaten, returning us to health. In those with allergies, however, these symptoms are prolonged; as long as you’re exposed to the triggers, the symptoms continue.

Cells on the Attack

When it comes to fighting respiratory invaders, specialized cells are at work:

Basophils are immune cells that circulate in the body and travel to entry sites for invaders. In those with allergies, when an allergen like ragweed or pollen enters the body, basophils are sent to the site (e.g., the nasal passages or eyes) where they release histamine. It’s histamine that triggers sneezing and coughing, as well as the contraction of the muscles in the lungs, causing difficulty breathing and sometimes wheezing. The goal of histamine: to help the body get rid of the aggravating substance.

Eosinophils (e-o-SIN-o-phils) are another important type of immune cell involved in allergic and asthmatic reactions. These immune cells can trigger wheezing and bronchoconstriction, where the airways become narrower, blocking the flow of air and making it harder to breathe. Having too many eosinophils in a particular location (i.e., when someone has allergic asthma or eosinophilic esophagitis) isn’t good. In this case, too many of these immune cells can contribute to tissue damage and long-term inflammation.

Macrophages are some of the first immune cells at the scene of the invasion; some reside in tissue like the airways and others circulate in the bloodstream. These cells produce cytokines, which start the immune cascade to get us healthy. Like neutrophils (see below), these immune cells are scavengers; they’re designed to engulf harmful invaders and in the process, kill them.

Mast cells are types of immune cells found in tissue throughout the body, including under the skin, in the nasal passages, and in the lungs. They are the first line of defense against invaders, or triggers, entering the body. These cells are immediately activated by pathogens—be it a virus, bacteria, or an allergen— and initiate inflammation by secreting cytokines like histamine. It’s this natural chemical that makes the blood vessels expand and the surrounding skin itchy and swollen. It also triggers a build-up of mucus in, and a narrowing of, the airways.

Neutrophils are immune cells recruited quickly to the lungs when there’s a respiratory infection. These cells—which live less than 24 hours—are recruited to kill invaders, repair tissue damage if necessary, help reduce inflammation, and be finished. Like macrophages, neutrophils are phagocytes: they’re Pac- Man-like cells that gobble up or engulf pathogens in an attempt to kill them.


It’s estimated that each day 1 billion neutrophils are produced per every two pounds of body weight. This number can increase to 10 billion during an infection.

T cells are the most abundant white blood cells in the body and are a type of cell called lymphocytes. These immune cells play an essential role fighting infection-causing viruses and bacteria, as well as cancer cells. They actually kill the cells in the body that have been overtaken by viruses and in doing so, help to clear up the infection.

While not technically an immune cell, goblet cells (so-called because of their goblet-like shape) are other important cells involved in the immune response. These cells—some of which are found in the nasal passages—secrete something called mucins, which are components of mucus. Mucus is produced by these cells in an attempt to protect the mucous membranes from the invader and rid the body of it.


The mucin gel in goblet cells can expand up to 500 times its original volume in just 20 milliseconds, which is why—when you first get a respiratory virus—congestion can develop very quickly.

Keeping Your Immune System Healthy

When your body is healthy, your immune system is healthy and it’s better able to fight off harmful pathogens like viruses or bacteria that can make us sick. The same things that keep us healthy also keep the immune cells in fighting condition. These include:

MOVE YOUR BODY REGULARLY for at least 30 minutes daily. This boosts circulation and flow of the lymphatic system, part of the immune system that produces, releases, and distributes immune cells throughout the body. Moving these immune cells effectively around the body is essential to stopping the spread of sickness and infections.

GET SOME SUNLIGHT to get more vitamin D. When UV light shines on the skin, the epidermis, or outer layer of skin, converts a substance in the skin to vitamin D3. This vitamin is critical to immune function. Typically 15 minutes of unprotected sunlight during the late spring and summer is the amount necessary to create enough vitamin D3 for the body, but those with darker skin typically need up to three times this amount to get enough vitamin D3.

SLEEP SOUNDLY for at least seven hours every night. It’s during sleep that our cells repair themselves and the body relaxes and rejuvenates itself. Not getting enough quality shut-eye can trigger inflammation. Strategies that can help: skip before-bed news (too stressful), ban phone scrolling at least an hour before bed, avoid caffeine after 3 p.m., and dim bedroom lights about an hour before bed to set the stage for sleep.

FIND WAYS TO DE-STRESS to help lower overall inflammation. Anxiety and stress are key drivers of inflammation. Meditation, yoga, mindful walking, and even creative activities like painting or journaling can help.

EAT A NUTRIENT-RICH DIET which can feed immune cells the nutrients they need to function optimally, replicate quickly to create a powerful army to fight off invaders, and give them the energy they need to do their job. Diet is the number one tool for keeping your immune system in optimal condition all year long.