Fergus Farrelly woke up on 7 January at his mother’s house in Cavan, Ireland, when he noticed a ‘marble-sized’ lump on his private parts.
The 26-year-old initially dismissed it, but over the next few days the lump grew bigger and bigger.
On the third day, he was finally persuaded to go to A&E after the lump had reached the size of a golf ball and was turning purple.
Fergus said: "I had no idea what it was. When I first went to hospital, the doctors didn't know either.
"It was this constant burning pain and the lump kept getting bigger and bigger."
To make matters worse, just hours after he arrived in A&E, the huge cyst burst, leaving a giant hole where it had once been.
Over the next few days, doctors ran a number of tests on Fergus and finally spotted the venom of a black widow spider in his blood tests.
False widow spiders are now increasingly common across Ireland and share a similar toxin to the black widow – about two thirds as powerful.
Fergus said: "I couldn't believe it when they found the venom of a black widow spider in my blood – I'd never even heard of one before.”
While their venom is rarely fatal, a black widow’s bite can cause muscle cramps and pain so intense it can be compared to appendicitis or a heart attack.
Fergus continued: "I got told I would probably have ended up dead if it hadn't burst in the hospital because it would likely have got infected.
"They said the venom could have spread and poisoned my blood system."
Luckily, Fergus was treated quickly and dressings were applied to protect the wound by specialists who said 'they’d never seen anything like it before'.
Four days later he was discharged, although he has now been left with a 2cm scar.
Reflecting on the horrifying and painful experience, Fergus admitted he feared the worst.
He said: "I was convinced I would lose my penis. The doctors didn't know any more than me and have never seen a bite down there, so I was very worried.
"The pain was unbearable too."
But looking back, he added: "I do find it a wee bit funny now because it is unusual. But it's also really scary – I had no idea what damage spiders could do."
Featured Image Credit: SWNS