What does eating snow do to the body?

December 26, 2025 •

3 min read

According to scientific studies, even in apparently pristine environments, snow can contain bacteria and other microorganisms. For this reason, and others related to temperature and energy expenditure, consuming snow is not the simple and pure source of hydration many assume it to be. Instead, it poses several risks to the body, including illness and reduced body temperature.

Quick Summary

Consuming snow poses risks including dehydration, a drop in core body temperature, and the ingestion of pollutants, bacteria, or other contaminants from the air and ground.

Key Points

Dehydration Risk: Consuming snow can actually dehydrate the body, as more energy is expended to melt it than the fluid gained.
Hypothermia Danger: Eating large amounts of cold snow lowers core body temperature, increasing the risk of hypothermia.
Contamination Is Common: Snow is not pure and can pick up airborne pollutants like chemicals and black carbon, even in remote areas.
Ground Contaminants: Snow that has been on the ground can contain bacteria from animal waste, as well as de-icing chemicals and other debris.
Safer Hydration: The safest way to consume snow for hydration is to melt and boil it to kill pathogens and avoid temperature shock.

The Myth of Pure Snow: A Closer Look at Contamination

Many people believe that freshly fallen, white snow is pure and safe to consume, but this is a common misconception. As snow falls through the atmosphere, it acts as a natural air filter, locking in various pollutants and microscopic particles. These contaminants can include industrial emissions, vehicle exhaust, and other airborne particles. Furthermore, once snow settles on the ground, it can absorb even more contaminants from the surface.

Types of Contamination in Snow

Industrial Pollutants: Snow can pick up harmful chemicals like sulphur dioxide, nitrogen oxides, and ammonia released by factories and power stations.
Vehicle Exhaust: In urban areas, snow absorbs black carbon particles and heavy metals, such as lead (historically) and cadmium, from car emissions.
Animal Waste and Bacteria: Snow on the ground is easily contaminated by animal feces and urine, which can introduce harmful bacteria like Escherichia coli and Salmonella.
Pesticides and Microplastics: Wind can carry pesticides from agricultural areas or tiny microplastic particles over vast distances, contaminating snow even in remote regions.
Colored Snow: Unusual colors, like yellow, red, orange, or green, are often clear warning signs of significant contamination from urine, algae, or mineral dust.

The Dehydration Paradox: Why Eating Snow Isn't Hydrating

Contrary to intuitive belief, consuming large quantities of cold snow can actually cause dehydration. The body must expend a significant amount of energy to melt the frozen water and warm it to body temperature for digestion. This metabolic process consumes more fluids than the body extracts from the snow, creating a net loss of hydration. In a survival situation, this is especially dangerous as it depletes a person's vital energy reserves.

Risk of Hypothermia

Eating large amounts of cold snow can significantly lower a person's core body temperature, increasing the risk of hypothermia. When the body is already working hard to stay warm in a cold environment, the added stress of melting snow can be a tipping point. This is a particular concern for vulnerable groups, such as children and thinner individuals, who have less body fat for insulation.

Impact on Digestion and Kidneys

Ingesting cold, contaminated snow can lead to various gastrointestinal issues. The low temperature can irritate the digestive tract, potentially causing stomach cramps, bloating, or diarrhea. Ingesting contaminants or bacteria, such as E. coli, further increases the risk of sickness and infections. The minerals and pollutants picked up by the snow can also place an unnecessary burden on the kidneys, which must work to filter out these substances.

Safer Hydration Practices: Eating Snow vs. Melting Snow

When faced with a lack of drinking water, especially in a survival scenario, melting and boiling snow is the far safer option. The following table compares the risks and benefits of eating snow directly versus melting it properly.


Aspect	Eating Snow Directly	Melting and Boiling Snow
Hydration Efficiency	Inefficient; can cause dehydration due to energy expenditure.	Highly efficient; provides clean, warm water for rehydration.
Contamination Risk	High; potential for ingesting pollutants and bacteria.	Low; boiling kills most pathogens and purification can remove others.
Hypothermia Risk	High; lowers core body temperature, depleting energy.	Very Low; provides a warm beverage that can help raise body temperature.
Digestive Impact	Potential for irritation and illness from coldness and contaminants.	Gentle on the digestive system; prevents stomach upset caused by cold water.
Electrolytes	Provides none.	Can be added back with electrolytes or food after preparation.

For more detailed advice on wilderness hydration, survival guides are an excellent resource, often recommending boiling any water source.

Conclusion: The Bottom Line on Eating Snow

While a small, single taste of freshly fallen, white snow in a clean, rural area is unlikely to cause serious harm, relying on snow for hydration is a significant risk. The body's need to expend energy to melt it can lead to dehydration and lower your core temperature, while the inherent risk of unseen contaminants can cause illness. For true hydration and safety, always melt and purify snow before consumption, especially in survival situations or areas with potential pollution.

Frequently Asked Questions

While small amounts of fresh, white snow are generally not a major health risk, it is never truly pure. As snow falls, it collects pollutants and microorganisms from the atmosphere, meaning even clean-looking snow can be contaminated.

No, it's counterproductive. Your body uses more energy and fluids to melt and warm the snow than the liquid you get from it. This can worsen dehydration and drain your energy reserves.

The immediate effect depends on the type and concentration of contaminants. You might experience a stomachache, bloating, or diarrhea due to bacteria like E. coli or chemical exposure. Ingesting large quantities increases health risks.

Consuming large quantities of snow forces your body to expend significant heat and energy to melt the cold water. This can cause a drop in your core body temperature, increasing the risk of hypothermia, especially in an already cold environment.

Colored snow is a strong indicator of contamination. Yellow snow often contains animal urine, while red or green colors can be caused by algae or other substances. Orange or brown hues can signal industrial pollutants or wind-carried dust.

Melting snow does not remove contaminants. For the safest water, you should melt and boil the snow for at least one minute to kill any bacteria or viruses present.

The safest method is to collect clean, white snow from a rural area, melt it in a container, and then bring the water to a rolling boil for at least one minute to purify it before drinking.