Ally Hilfiger (pictured, with fashion designer father Tommy) is understood to have contracted the disease, which is carried and spread by ticks, when she was seven-years-old

The daughter of US fashion kingpin Tommy Hilfiger says Lyme disease left her living 'like an 80-year-old woman' after doctors failed to discover she had the debilitating illness for 14 years.

Ally Hilfiger is understood to have contracted the disease, which is carried and spread by ticks, when she was seven-years-old.

However, she claims she wasn't diagnosed properly until she was 21, leaving her young body ravaged by the condition.

Speaking to the Daily Mail's Sebastian Shakespeare, Ally said: 'I couldn't put lotion on my legs because it felt as if I was being beaten with a baseball bat. I was like an 80-year-old woman.

'It had taken over every single cell in my body and in my brain.'

The 30-year-old was bitten by a tick as a child but the insect tested negative for Lyme disease, as did later medical exams.

However, some results were 'borderline positive', she said.

Undiagnosed, the fashion heiress suffered with the disease's crippling symptoms - which include chronic fatigue, headaches and muscle pain - for almost two decades.

She described the pain as 'excruciating', detailing how it would often leave her sitting in the bath for hours or walking with a stick. She also had flu-like symptoms and trouble sleeping.

Speaking openly, she insists she was misdiagnosed for 14 of the 19 years she suffered with the illness, with doctors suspecting her ill-health was being brought on by arthritis or, simpler still, growing pains.

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Unconvinced, she eventually saw a psychologist who was familiar with Lyme disease. She recognised the symptoms straight away and referred the fashion heiress to another doctor, who eventually confirmed the illness.

'This was like winning the lottery for me. I was so relieved,' said Ally.

The mother-of-one was photographed last week at the inaugural Global Lyme Alliance gala.

The fashion heiress (left, with former supermodel Yolanda Foster) suffered with the disease's crippling symptoms - for almost two decades. Foster has Lyme disease, and admitted last week that her model daughter Bella, 18, (pictured together, right) also has the illness

Foster (second from right) revealed last week that two of her three children also have the disease - a bacterial infection spread to humans by infected blacklegged ticks, which are found in woodland areas and on pets

Others in attendance included supermodel Yolanda Foster, who was diagnosed with the condition in 2012.

WHAT IS LYME DISEASE? Lyme disease, or Lyme borreliosis, is a bacterial infection spread to humans by infected ticks. Ticks are tiny spider-like creatures found in woodland and heath areas throughout the UK and in other parts of Europe and North America. Many people with early-stage Lyme disease develop a distinctive circular rash at the site of the tick bite, usually around 3 to 30 days after being bitten. Some also experience flu-like symptoms in the early stages, such as tiredness, muscle pain, joint pain, headaches, fever, chills and neck stiffness. More serious symptoms may develop several weeks, months or even years later if Lyme disease is left untreated or is not treated early. These include pain and swelling of the joints, problems affecting the nervous system - including numbness and pain in the limbs - facial paralysis, memory problems and difficulty concentrating. Lyme disease can also lead to heart problems such as myocarditis, where the heart muscle becomes inflamed and heart failure. Meningitis is also a risk. A small minority of people go on to develop long-term symptoms similar to those of fibromyalgia or chronic fatigue syndrome, called post-infectious Lyme disease. Source: NHS Choices Advertisement

The 51-year-old revealed last week that two of her three children also have the disease - a bacterial infection spread to humans by infected blacklegged ticks, which are found in woodland areas and on pets.

Foster - star of reality series Real Housewives - opened-up about model daughter Bella, 18, and son Anwar Hadid, 16, both secretly battling Lyme disease for over three years.

Addressing the crowd in an emotional speech, Yolanda said: 'When my two youngest children, Bella and Anwar, were also diagnosed with chronic Lyme disease in early 2012, watching my babies struggle in silence in order to support me in my journey, struck the deepest core of hopelessness inside of me.'

Others suffering from Lyme's include the billionaire founder of Phones4U. John Caudwell, who has seen the disease rip through his entire family, affecting himself, his ex-wife and three children.

He attributed that to doctors not knowing that the disease can be transmitted between humans.

Having recovered from the illness - which is best treated if discovered early - Ally Hilfiger gave birth to a healthy daughter, clear of the disease, eight months ago.

She said: 'The only thing that kept me going was the hope that I would possibly one day become a mother.

'Today, I am proud to stand here and tell you I'm finally cured.'

The former reality TV star now says she wants to be help support other sufferers.

Ally added: 'People do need long-term antibiotic treatment. A lot of people don't understand what it feels like and they don't believe it. I'm a pretty tough cookie and I don't like complaining. It took a lot for me to say: "I'm in pain."

Family illness: Phones 4u founder John Caudwell with his two daughters Rebecca (left) and Rhiannon who all have been diagnosed with Lyme disease; Mr Caudwell believes that the disease is endemic, arguing that if an entire family can be infected, the disease must be both sexually transmitted and passed from mother to child

'It's been a challenging road and I think what got me out of bed some days and kept me fighting was so I could help people one day.'

The number of confirmed cases of Lyme Disease in the UK has quadrupled in just 12 years, with more than 1,000 people diagnosed with the condition in 2013.