Spring is supposed to be the feel-good season. The days get longer, temperatures rise, and the worst of cold and flu season is supposed to be behind us. So why do so many people find themselves sick right as the weather turns?

It turns out early spring has its own distinct biology of illness, and it is not simply a continuation of winter sickness. A separate set of factors converges in this window, and understanding them offers a clearer picture of what is actually happening in the body and what can be done about it.

Rhinovirus Has Two Peaks, and Spring Is One of Them

Most people associate colds and respiratory illness with winter, and that association is largely correct for influenza. But the human rhinovirus, the most common cause of the common cold worldwide, follows a different pattern. Research consistently shows that rhinovirus circulation peaks twice per year in temperate climates: once in autumn and again in spring.

A 2025 review published in Respiratory Research confirmed that rhinovirus has peak incidence in spring and autumn, and that it persists and circulates even when other respiratory viruses decline. Unlike influenza, rhinovirus does not disappear when temperatures warm. It thrives in the mild, transitional conditions that define early spring, which is precisely when many people let their guard down, assuming illness season is over.

This is an important distinction. Spring illness is often not the tail end of winter sickness. In many cases, it is a rhinovirus wave with its own seasonal rhythm, driven by a different set of conditions than those of the flu outbreaks in December and January.

Allergies and Viral Infections: A Crowded Intersection

Spring pollen season and the rhinovirus peak occur roughly at the same time, and the overlap is not coincidental in its impact on health. According to the CDC, nearly 26% of American adults have seasonal allergies. When pollen triggers an immune response, the resulting inflammation in the nasal passages creates conditions that make it easier for viruses to establish an infection.

Research published in Medical Economics notes that the layers of exposure compound. A person with baseline inflammation from allergies has a lower threshold for viral infection. If a recent illness has already inflamed the airways, the arrival of pollen season can push the immune system further into an overloaded state. The result is that allergy sufferers are at meaningfully elevated risk of also catching a cold during this period, not because their immune systems are weaker, but because their airways are already dealing with a significant inflammatory burden.

Even for people without allergies, seasonal shifts in barometric pressure, temperature, and wind can irritate nasal passages and reduce the effectiveness of the nose’s first-line defenses against inhaled pathogens.

What Cold Air Actually Does to Your Nose

One of the more striking recent findings in respiratory immunology came from a 2022 study published in the Journal of Allergy and Clinical Immunology by researchers at Mass Eye and Ear and Northeastern University. The study identified a previously unknown immune mechanism in the nasal passages: when bacteria or viruses are inhaled, cells at the front of the nose release billions of tiny fluid-filled structures called extracellular vesicles into the mucus. These vesicles swarm the pathogen and contain antiviral proteins that neutralize threats before they can enter the body.

The same research team then tested how this response changes at colder temperatures. After healthy volunteers were exposed to about 4 degrees Celsius for 15 minutes, the internal temperature of the nose dropped by roughly 5 degrees. At that reduced temperature, the quantity of protective extracellular vesicles secreted by nasal cells fell by nearly 42 percent, and the antiviral proteins they carried were also impaired.

In early spring, outdoor temperatures are still cool enough to trigger this effect, particularly in the morning and evening hours. The nose has not yet returned to the warmer, more protective internal environment of summer. That partial, fluctuating vulnerability is a meaningful contributor to spring illness rates.

It Is Not That Your Immune System Is Weak

A common framing of seasonal illness is that the immune system is depleted or weakened in spring. Recent research suggests this is an oversimplification. A 2025 paper in the Southeast European Journal of Public Health found that immune fitness does not vary significantly across seasons in healthy individuals. What changes between seasons is not immune capacity so much as the volume and nature of challenges the immune system is asked to respond to.

In early spring, the immune system may be handling rhinovirus exposure, pollen-driven allergic inflammation, residual effects of winter vitamin D deficiency, and disrupted sleep from shifting daylight patterns all at once. The problem is not a weakened defense. It is an unusually high number of simultaneous demands. This distinction matters because it shifts the practical focus from “boost your immune system” to “reduce the load your immune system is managing.”

Targeted Strategies for Spring Wellness

Given the specific biology of spring illness, a few targeted strategies are more relevant than general wellness advice.

Protect the nasal environment. Keeping the nasal passages warm and moist directly supports the immune mechanism described above. Staying hydrated helps maintain mucosal function. A saline nasal rinse can clear allergens and pathogens from the nasal passages before they have a chance to establish an infection. On cool mornings, keeping a scarf loosely around the nose during outdoor activity is a low-effort way to maintain nasal temperature.

Address the allergy burden early. For people who experience spring allergies, starting antihistamines or nasal corticosteroid sprays before pollen season peaks (rather than after symptoms appear) reduces the inflammatory load that makes viral infections more likely to take hold. Managing allergies proactively is, in effect, a cold-prevention strategy.

Prioritize sleep through the transition. Daylight extending into the evening disrupts the onset of melatonin production, which in turn delays sleep. This circadian disruption is a documented immune stressor. Using blackout curtains and maintaining consistent sleep and wake times through March and April supports immune function during a period when sleep is naturally under pressure.

Use targeted nutritional support. Vitamin D levels are typically at their annual low in late winter and early spring after months of reduced sun exposure. Deficiency is associated with increased susceptibility to respiratory infection. Zinc supports mucosal immune function and is widely used at the onset of cold symptoms, with reasonable evidence supporting its use. Both are worth considering during this specific window.

Consider herbal support for this seasonal window. Several herbs have a substantial body of clinical research supporting their use for upper respiratory support. Echinacea (particularly Echinacea purpurea and Echinacea angustifolia) is among the most widely researched herbs in this area, with studies examining its use during cold and flu season. Echinacea tincture preparations are generally considered well-absorbed formats for this herb. Elderberry has attracted substantial research interest and is widely used to support acute illness. Andrographis, less well known but with a growing evidence base, has been the subject of multiple clinical trials. These herbs are generally most relevant at the onset of symptoms or during high-exposure periods rather than as a continuous protocol throughout the year.

Spring Sickness Is Predictable, Which Means It Is Manageable

Early spring illness follows a pattern grounded in real biology: a rhinovirus seasonal peak, an overlap of allergy and viral inflammation, impaired nasal immunity in fluctuating cool temperatures, and circadian disruption from lengthening days. None of these factors is unpredictable, and none requires an extreme response.

The people who tend to stay well through spring are not those with unusually robust immune systems. They are the ones who understand that this window has its own specific demands, and who make a handful of well-timed adjustments in response.

Disclaimer: This article is for informational purposes only and is not intended as medical advice. Consult a qualified healthcare professional before beginning any supplement regimen or making changes to your health routine.