Beau Avis, who was already spooked by snakes before the incident, is now trying to raise awareness about the dangers of adders (Picture: Beau Avis/SWNS)

A dog walker terrified of snakes can no longer walk after being bitten by Britain’s only venomous snake, turning her leg yellow.

Beau Avis, 26, was out walking her pet cockapoo Bonnie with her dad Kevin Avis, 59, when an adder sunk its teeth into her ankle in Upminster, Essex.

She watched in horror as her leg began to swell up before suffering an anaphylactic shock, a life-threatening allergic reaction.

Taken to Queen’s Hospital in Romford, Beau was kept in for two nights after a doctor, by chance, had an anti-venom shot on May 31.

The rattling incident has left Beau unable to walk, being discharged from the hospital in a wheelchair.

Beau, from Brentwood, Essex, had taken Bonnie out at a woodland area during her lunch break at around 2pm.

The PR executive’s leg yellowed moments after the bite (Picture: Beau Avis / SWNS)

Beau found three bite marks on her left ankle (Picture: Beau Avis / SWNS)

The PR executive stepped out of the house in sandals only to end up treading on an adder while walking down a country path.

‘The bite felt like someone had poured acid into my left leg,’ said Beau.

‘I panicked as I’ve been scared of snakes my whole life – but I found out later panicking makes the venom spread faster.

‘In that scenario, you are supposed to stay calm – something I didn’t do!’

Beau looked down to see a 50cm adder snaking off, leaving behind three teeth marks on her left ankle.

Adders, also called European vipers, call woodlands and grasslands home and are known for their dark zig-zagging stripe down their up to 80cm long bodies.

‘I was freaking out and dad was desperately trying to calm me down – but the fear had already gripped a hold of me,’ she said.

She had to be kept in overnight so two shots could be administered (Picture: Beau Avis / SWNS)

‘We rushed back to the car and the pain and swelling was getting worse every second that went by – it was horrific.’

Paramedics arrived 25 minutes later to find Beau experiencing anaphylactic shock, with her drifting in and out of consciousness, vomiting and suffering stomach pain.

Officials from the National Poisons Information Services, part of the UK Health Security Agency, told doctors to mix together certain medicines to make an anti-venom adrenaline shot.

‘Thankfully they had the drugs they needed in the hospital and they blended a concentrate into an intervenes drip which fed into a bag,’ Beau said.

She was given the shot at around 4pm but by the evening, Beau’s ‘whole limb was bright red and had doubled in size’, she said.

Beau had to get another at 6am the following day to ‘flush’ the poison out. She now has to relearn how to walk after the venom tore through her leg.

The bite felt like ‘acid’, she said (Picture: Beau Avis / SWNS)

‘An adder bite hasn’t killed anyone in ages, but they were really concerned in the first 12 hours because of my low blood pressure,’ she said.

‘If I’d have known panicking spreads the venom, I would have done more to stay calm.

‘That’s why I want to share my story so others know how to react if they ever get in a similar situation.’

According to The Wildlife Trusts, adders are stocky and secretive snakes that can be found slithering in most parts of the UK other than Northern Ireland.

‘The adder is the UK’s only venomous snake, but its venom is generally of little danger to humans: an adder bite can be painful and cause inflammation, but is really only dangerous to the very young, ill or old,’ the charity says on its website.

‘If bitten, medical attention should be sought immediately, however.’

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‘The bite felt like someone had poured acid into my left leg.’