The severe storms that have battered the east coast have left several beaches covered in sea foam - but there's a good reason to steer clear of the phenomenon.

So far, the bulk of the foam has turned up on beaches in the Northern Rivers region of NSW and on the Gold and Sunshine coasts, attracting crowds of curious locals.

The foam also went viral across the globe after a local Byron Bay woman interrupted a live weather update to search for her missing dog, Hazel, who was later rescued from the mess.

According to the National Oceanic and Atmospheric Administration (NOAA), sea foam forms when organic and artificial matter in the ocean is agitated by wind and waves.

And while the foam itself is usually harmless and non-toxic, it turns out the substance - which is also known as "spume" - can contain a string of hidden dangers.

SEA SNAKES

The biggest concern by far is sea snakes, which can be concealed beneath the foam.

The thick layer means any lurking sea snakes are well and truly hidden - and while they are generally non-aggressive, they are also highly venomous, meaning a bite could be fatal.

In 2015, Far North Coast surf lifesaving director Ben Redman told The Northern Star people "shouldn't swim in it".

"You'll usually find a lot of sea snakes in the foam, they seem to be attracted to it," he told the publication.

In fact, Mr Redman claimed that in 2008, 21 snakes were counted during a foam event at Ballina's Lighthouse Beach.

POLLUTION AND VIRUSES

The foam can also contain other nasties, including pollution and viruses

According to the NOAA, "when large harmful algal blooms decay near shore, there are potential for impacts to human health and the environment".

"Along Gulf coast beaches during blooms of Karenia brevis, for example, popping sea foam bubbles are one way that algal toxins become airborne," the website warns.

"The resulting aerosol can irritate the eyes of beach goers and poses a health risk for those with asthma or other respiratory conditions."

DROWNING TRAGEDY

In May this year, five Dutch surfers aged in their 20s and 30s died after being overcome by freak swell conditions created by a sea foam "avalanche".

While all five were experienced, they were unable to cope with the combination of wild weather, winds and swells and the unusually thick layer of foam that drifted on the North Sea waters by the beaches at Scheveningen, a suburb of The Hague.

Originally published as Hidden danger lurking in storm foam