Simon John, 45, said he and his five-month-old baby Harrison were bitten during the night by the spider as the family slept during the break.
The next morning Mr John was unaware of the bite, blaming his fever on being hungover and returned home with his family from Breen, Somerset.
But two days later at home in Newport, South Wales, he noticed two nasty red marks on his leg which quickly began to swell.
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Tiny Harrison also had a fever and so they dashed to hospital where they quickly treated the pair.
The baby”s condition improved but although his father was given strong antibiotics, his wound began to grow in size.
Baffled doctors rushed Mr John to have a CT scan where they discovered the cause of his problems – a deadly spider bite.
It had caused an open hole to appear on his leg and the flesh began to rot.
But quick-thinking medics managed to save the limb and ultimately his life.
Mr John, a window fitter, said: “It was really scary. I was rushed to intensive care after doctors realised it was a spider bite that was causing my severe leg pain.
“It wasn”t until the Monday, two days later, when I noticed red marks coming up from the veins in my upper leg that I thought I was in serious trouble.
“I rushed myself to the hospital and was put on a drip, but I was still suffering from unbearable pain.
“The doctors immediately put me in for a scan, then out of nowhere I was in intensive care, there were cables and tubes everywhere.
“The fact they put me through for a scan straight away made me so worried, because usually they take weeks.
“I was told by a doctor that I was bitten by a spider, but they didn”t know the type of spider or how bad my leg would get.”
Mr John was unable to see his wife Stephanie, 25, and children Harrison, five months, James, four, and Jack, six, and his two older children while the treatment continued.
Finally after two weeks in hospital, he was discharged and is now on the slow road to recovery.
Since being bitten, he has been placed on numerous medication to numb the pain, but says he still struggles to walk on his leg three months later.
Mr John said: “Harrison was also in hospital for a few days and my wife was with him, I couldn”t see the two of them and my head was in 1000 places.
“I was given Flucloxacillin tablets and I had loads of stomach injections to protect my upper body.
“I have been to the hospital two days a week since the incident and thankfully I”m on the mend.
“I was due to have plastic surgery next month but that”s been called off because of how well I”m recovering.
“However it has been three months and I still have struggles when walking, I still need my crutches.”
The father-of-five says he has warned the holiday park of his spider bite and hopes others will take his story as a warning.
Mr John said: “When I go back to the hospital now and people find out I have a spider bite they all want to see my wound.
“Everyone is desperate to see my leg which I don”t mind showing now I”m getting better.
“I warned the holiday park about the incident and they were so shocked, there have been no other incidents like it in the area which is staggering.
“Thankfully the doctors that I have dealt with have been a huge help, essentially they”ve saved my life.”
There was an influx of spiders invading British homes this summer due to the hot weather.
Earlier this week, an eight-year-old girl was left with a hole in her hand after being bitten by a spider.