John Travolta's oldest son Jett, who died suddenly at the family's holiday home in Nassau in the Bahamas, had a long history of seizures dating back to when he was two years old.
Jett, 16, was diagnosed with Kawasaki disease 16 years ago, leading his parents to blame the chemicals in household cleaners and fertilisers.
Travola, 54, and his wife, Kelly Preston, 46, put their son on a detoxification programme based on teachings from the Church of Scientology, but it is not clear if he was also given other medication.
The star couple are both practising Scientologists along with other members of the Hollywood A list including Tom Cruise and his wife Katie Holmes.
Loretta Mackey, the police spokeswoman in Nassau, said Jett had hit his head while in the bath. He was discovered unconscious and taken to hospital, but was declared dead on arrival.
The police said they were planning an autopsy to determine the cause of death.
Travolta's attorney, Michael Ossi, said that the teenager's death "was completely out of the blue".
He added: "This is the worst day of John's life."
After an autopsy the body will be buried in Ocala, Florida, close to where the family lives.
They had been staying in their property at the Old Bahama Bay resort community on Grand Bahama Island.
Robert Gidel, president of Ginn Resorts, the property's owner, said: "The Travolta family has become like family to us at Old Bahama Bay and we extend our deepest sympathies to them."
Jett was the eldest child of the star of Grease, Saturday Night Fever and Pulp Fiction and his wife, the actress Kelly Preston.
The couple also have a daughter, Ella Blue, who was born in 2000.
Travolta is a qualified pilot and has flown for the Australian airline Qantas when not fulfilling his Hollywood commitments. Such is his enthusiasm for aviation that he persuaded his wife to name their son Jett.
Travolta, his wife Kelly, and Ella Blue were all due to star alongside Robin Williams in a new comedy, Old Dogs, this year.
Unlike his sister, Jett had shown no enthusiasm for following his parents into acting and was interested more in the outdoors and physical pursuits.
"As much as Ella loves showbusiness, he loves the outdoors – sports, swimming, cycling, hiking," the film star has said.
- telegraph.co.uk