Why Does Saltwater Burn Your Eyes When Swimming?

If you've ever felt the agony of saltwater in your eyes while swimming at the beach, you may have wondered about the science behind this unpleasant sensation.

Although tears and saltwater are both salty, they elicit different responses due to their varying compositions.

Tears contain water, oils, mucus, proteins, minerals, and salt, but their salt content is approximately 0.9%, which is close to the body's cell concentration.

On the other hand, seawater comprises about 3.5% salt, making it nearly four times saltier than tears.

When saltwater enters the eyes, the higher salinity causes the cells to lose moisture through osmosis, resulting in the discomfort and irritation experienced.

This process of osmosis involves the movement of solvent molecules through a semipermeable membrane, causing the eyes to become red and inflamed.

To avoid this unpleasant experience, wearing goggles or a diving mask while swimming in the ocean can prevent saltwater from reaching the eyes, ensuring a more enjoyable and pain-free experience.