Pool shock is the application of extra chlorine to the water to kill harmful bacteria and algae. Chlorine is a highly reactive and corrosive oxidizer. If you enter the water while a pool is being shocked, while chlorine levels are too high or while undissolved chlorine products are present, you risk skin damage and other injuries.
Chlorine is well established as an effective water disinfectant. During pool shocking, you might encounter chlorine in gas or solid form, or dissolved in water. The most common form of pool chlorine is calcium hypochlorite in a powder or solid tablet.
The greatest risk of harm to your skin is exposure to newly dissolved chlorine chemicals during pool shock treatment, or contact with spilled or unmixed powder. Direct contact with chlorinating chemicals such as calcium hypochlorite can cause serious chemical burns. Exposed areas should be washed off immediately with water.
Mechanism of Injury
Calcium hypochlorite reacts strongly with oils and moisture in the skin. In a process called liquifaction necrosis, the fats and protiens of your skin are destroyed, causing deep chemical burns that might have a delayed onset. In addition, toxic chlorine gas is released during this reaction. According to the Occupational Safety and Health Administration, chronic exposure to low levels of chlorine gas can result in a dermatitis known as chloracne.
Skin damage from pool shock can be avoided by staying out of the water until chlorine levels have dropped to normal. Because chlorine is broken down by sunlight, most pool managers shock at night to increase efficiency. By morning, chlorine levels are safe for swimming. Be alert for spilled powders, chalky looking pellets or other chemicals, and avoid contact.
Alternative water disinfectants are available, but chlorine remains in wide use. If you must shock during daylight hours, place a “Pool Closed” sign and keeping swimmers out. High levels of chlorine in the water dry and irritate skin. If you feel a burning or itching sensation when swimming, ask to see the water's chlorine level. Be sure to rinse off after swimming to prevent any residue from continuing to irritate the skin, then apply a moisturizing lotion.