Aussies stumped by mysterious rash after swimming at popular beaches

Experts have been unable to determine what caused the rashes.

A number of Sydneysiders have been left with similar looking bite or sting marks on their skin after swimming at various beaches this summer, with experts unsure what caused them or if the swimmers have even been afflicted by the same thing.

The latest incident occurred on Sunday after a swimmer, pictured below right, emerged from Clovelly Beach in Sydney's east with red blotches across her legs and feet. She questioned what had caused them, given she hadn't felt any discomfort or pain in the water.

Left, a man had tiny bumps on his forearm after swimming in a northern Sydney beach. Right, a woman had a weird rash consisting of red blotches all over her arms after swimming at Clovelly beach.
Sydneysiders have been complaining of weird rashes appearing on their bodies after swimming at local beaches. Source: Facebook

Two male swimmers had a similar experience at the end of last month when they arrived home from an unspecific beach in Sydney's north only to find their arms and backs covered by tiny raised bumps. A 16-year old boy found "itchy hives" all over his arms and hands after he swam at Collins Beach at Manly in Sydney's north.

"When he came out from his room the following day he said, 'Mum, I am dying, my body is burning, stinging, itching," his mum Soo Jung Lee told Yahoo News. "He grabbed the sand and swam in the ocean... the doctor said he was definitely bitten by something."

'No reliable answer' behind bites, experts say

Experts at the Queensland Museum reviewed the images and concluded it was "hard to know exactly what the cause could have been" but guessed sand flies, a type of biting midge, may be the most likely culprits.

"[We] would tend to gravitate towards sand flies for the reason that it is a typical reaction to not really notice the bites, but to get a delayed itchy localised hive response," a spokesperson for the Museum told Yahoo News.

Left, an image of the people on Bondi beach. Right, tiny sand flies on a man's body, appearing as small specs against the skin irritated skin.
Sand flies are found across Australia but are difficult to detect due to their small size. Source: Getty and Environmental Health Australia

Sand flies are so tiny they often go undetected and are the smallest of blood-sucking flies, found across Australia, according to the Australian Museum. They bite any exposed skin but each of the afflicted beachgoers had localised bites, making experts wary to confirm these insects were behind the skin irritations — suggesting a crustacean instead could have caused it.

"It is possible, although rare, for crustaceans such as scavenging amphipods or isopods to bite swimmers... [it is] unlikely to result in an allergic histamine response on the skin," the spokesperson said.

"Bottom line is we think there is probably no reliable answer after the event.”

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