Gold Coast resident Kay Henry said she and husband Jack had for three years planned a motorcycle trip around the deep South with two Dunedin friends.
When the couple, both in their early 60s, rented the three-wheeled motorcycle in Christchurch for their 12-day trip, Mrs Henry noticed a small spot on her upper left leg.
After a night in Fairlie, she stopped to swim in a Tekapo hot-pool and that night in Wanaka saw the spot was redder but believed rubbing from motorcycle leggings had created the irritation, Mrs Henry said.
However, when they reached Te Anau on Labour Day she began feeling hot and shivery despite her temperature being normal, she said.
The couple believed the sore was a spider bite and laughed at the irony of an Australian being bitten by a spider in New Zealand.
But fellow biker and friend Gordon Hunt, from Belleknowes, recognised the skin infection and urged prompt medical attention.
A Te Anau doctor confirmed it was cellulitis, prescribed oral antibiotics and they continued their holiday.
Despite some soreness, she felt fine, she said.
However, on Wednesday while visiting Cosy Nook, near Orepuki, the pain was "raging" so they headed for Southland Hospital in Invercargill, she said.
The doctor told her the motorcycling was over, gave her intravenous antibiotics and admitted her to hospital.
The next morning, a nurse cut each side of the hard white boil on her leg to release the "poison". But when it continued to fester, a doctor operated in the afternoon, she said.
She finally left hospital on Sunday and was driven to Dunedin.
She began bleeding again yesterday and was stitched up in Dunedin Hospital before flying to Christchurch. Mr Henry rode the motorcycle.
Their flight home to the Gold Coast today had been upgraded to business class so she could stretch out her leg, she said.
The couple had nearly forgone buying insurance because they were only travelling to New Zealand, she said.
"Thank God we did."
Mr Henry said he had never heard of cellulitis and was thankful Mr Hunt knew about the skin infection.
"If we hadn't had Gordon there to say 'don't muck around with this,' who knows what would have happened?"
Southern District Health Board vascular surgeon Andre van Rij said cellulitis was very common and very severe infections could cause kidney failure, the loss of affected limbs and death.
Some bacteria could spread very rapidly, within a few hours, Prof van Rij said.
What is cellulitis?
• A spreading bacterial infection of the skin and the tissue beneath.
• The bacteria enters small breaks in the skin but can occur in skin that is not obviously injured.
• Usually develops on the legs but can occur anywhere.
• Symptoms are redness, pain and tenderness of the skin.
• Infected skin becomes hot, slightly swollen and blisters with fluid may appear.
• Most people feel mildly ill with fever, chills, rapid heart rate, headache, low blood pressure and confusion.