By Chris Deziel, Updated Mar 24, 2022

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Applying salt to ice that contacts the skin can produce a chilling burn. Rather than a heat‑based injury, the damage stems from frostbite caused by the lowered melting point of ice.

Why Salt Lowers Ice’s Melting Point

Salt depresses the temperature at which ice melts, a principle that explains why roads are salted in winter and why the freezing point of a water–salt mixture is 32 °F on the Fahrenheit scale, while it is 0 °C for pure water. Traditional ice‑cream makers rely on this effect to freeze custard in a bucket surrounded by a salt‑laden ice bath.

How Salt Lowers the Temperature

When salt is added, the concentration of free water molecules in the liquid phase decreases, slowing the freezing process. The latent heat removed from the system remains the same, so the temperature must drop to compensate. The result is ice that feels noticeably colder against the skin.

When Ice Turns Into a Frostbite Hazard

A plain ice cube pressed to the skin keeps the surface at roughly 0 °C (32 °F), which can be uncomfortable but rarely causes frostbite. Introducing a layer of salt can drop the temperature to –21 °C (–6 °F) or lower, a level that can freeze skin tissues within minutes. The longer the contact, the higher the risk of permanent damage.

The Severity of Frostbite

Frostbite is classified into three degrees:

• First‑degree: tingling and discomfort; symptoms resolve after warming.
• Second‑degree: blisters form but eventually heal.
• Third‑degree: permanent tissue damage; the area may turn black or yellow, with loss of sensation until rewarming, followed by prolonged pain and possible scarring.

Understanding these risks can help prevent accidental cold burns. For detailed guidance, consult reputable sources such as the Mayo Clinic or the National Weather Service.