Which action is important when dealing with a casualty who has a severe burn?

When dealing with a casualty who has a severe burn, it is crucial to cool the burn immediately with cold water. This action helps to reduce the temperature of the burn area, alleviating pain and minimizing tissue damage. Cooling the burn also aids in preventing further injury to the skin, as it can help to stop the burning process and reduce inflammation and swelling.

Using cold water is a safe and effective method to manage burns, as it allows for a soothing effect and can assist in alleviating the initial shock the casualty may experience. It is generally recommended to run cool (but not ice-cold) water over the affected area for at least 10 to 20 minutes, ensuring that the water is not excessively cold to avoid further harm.

The other options are not appropriate for managing severe burns. Applying ice directly can lead to frostbite and further injury to the skin. Covering the burn with butter or oil may trap heat and bacteria against the skin, worsening the injury and creating a risk for infection. Leaving the burn exposed may lead to additional irritation and contamination from the environment, which could complicate the healing process. Therefore, cooling the burn with cold water is the most effective and appropriate first aid action.