Once a week, Lynda Lim wakes up with a terrible hangover. Her head pounds, her mouth and eyes feel dry and her fingers and stomach are strangely puffy and bloated.

But the 64-year-old actress isn’t suffering the effects of one too many gin and tonics. In fact, she rarely drinks.

Instead, Lynda’s hangover has a much stranger cause – salt.

Experts now say that having too much salt the night before causes many of the symptoms of a hangover. This is because both salt and alcohol leave you very dehydrated.

Put simply, dehydration occurs when the body loses more water than it takes in. This loss of water results in lack of moisture in areas where we notice it – such as the mouth, throat and eyes. But it also affects parts of the body we can’t necessarily see, but can definitely feel.

Water helps regulate the amount of blood in our bodies. When there’s less water in our bodies, there’s less water in our blood and blood pressure drops, making us feel lethargic.

This lack of blood pressure is also thought to be responsible for those hangover headaches, as less blood and oxygen reaches the brain, causing the blood vessels around the brain to dilate, resulting in swelling and pain.