Nuala and Paddy Lavin from Co Mayo believe in miracles because, to them, their nine-year-old son Seosamh is one.

Having been diagnosed with epilepsy as a baby, he was suffering up to a 100 seizures a day. His development was severely arrested. Nuala exlains: "He could only walk a few steps before falling -- he made very little eye contact and didn't interact with people at all. A lot of the drugs he was on made him worse; they didn't stop the seizures -- they knocked him out and made him very lethargic".

Two years ago, after much trial and error with a cocktail of medicines, their consultant at Dublin's Temple Street Hospital, Dr Mary King, said there was nothing more she could do for them.

"He was still having up to 50 seizures a day. We honestly thought he might die because, in hospital, you see children go to intensive care after massive seizures and never come out," says Nuala.

But now, due to the ketogenic diet being promoted by Great Ormond Street Hospital (GOSH) in London, their son is coming back to life. "Within one week his muscle tone improved, his speech improved, he could walk straight without falling and the number of seizures were right down. He is almost seizure-free now and his medication is being reduced."

The diet is similar to Atkins in that it is high in fat and protein, as well as very low-carb, in order to put the body into a fat-burning state known as ketosis. During ketosis the body produces ketones, which miraculously stop the seizures.

Dietician Caitriona Hensey, of Children's University Hospital, Temple Street, says it is a very complex balance and must only be tried under strict medical supervision.

"Because children are staying on this long term, we need to ensure they also get all the nutrients they need. The ketogenic diet is not only a huge undertaking for a parent, it could be very dangerous to the health of the child if carried out without the supervision of a medical team."

Esther Sexton of Blarney, Cork, feels she should have been told about the diet as a first option.

"I'm so angry we weren't told about the diet earlier. My other two children have seen horrendous seizures and it's left an awful mark on their lives."

Esther and Keith are parents to five-year-old Aoife, who was diagnosed with childhood epilepsy at the age of two. She was prescribed Epilim and sent home from the Mercy Hospital. However, Aoife's seizures got worse, progressing from one or two a day up to 50 or 60.

"After six months, Aoife was on a mixture of Epilim, Tegretol and Frisium, which seemed to ease her condition and she was down to one seizure a day. But then she got worse and was given Lamictal. It worked at first, but then the seizures came back and we were given Keppra. Again, there was a honeymoon period with reduced seizures but they came back."

With so many drugs in her young system, it wasn't long before the powerful side effects started to show.

"Aoife was knocked out, she was sleeping all the time and she couldn't concentrate. At night she was on Diazepam and all this is very bad for the liver. It's upsetting seeing what the drugs do to your child. We were then prescribed Topamax and two weeks later she was very bad. Her head would fall forward as if from an electric shock and then her whole body would follow, which she had never experienced before."

By this time, Esther desperately wanted an alternative. Through a friend she heard about the ketogenic diet in GOSH, London, and begged her consultant, Olivia O' Mahony, for a referral, not knowing it was available in Ireland. They were put on the waiting list for professor Helen Cross at GOSH, but were told it would be better to be on the diet closer to home.

"I phoned around all the hospitals and eventually found Caitriona Hensey at Temple Street Hospital, but she said they were completely snowed under. I wouldn't give up though and phoned again, but still they said no.

I then phoned Helen Cross in London and contacted Temple Street on our behalf, and the consultant Brian Lynch agreed to see us.

"We had our first appointment there last June and are now using the diet to come off the drugs. Aoife is already off Keppra and recently had her first seizure-free night in four years."

Aoife's condition has improved all round. Her speech is better, she can now hold a pencil properly and she is more alert, says Esther.

Their hope is to have Aoife off all drugs and seizure-free one day. She says: "I just wish someone had told me about the diet in the first place, because then I would never have let Aoife go on five different medications."

According to Emma Williams, founder of Matthew's Friends -- a support network of parents whose children are on the diet -- the ketogenic diet has been used for more than 80 years.

She says the introduction of anti-convulsant medication in the 1930s saw the diet take a back seat, and even now it is only used as a last resort.

It took her six years to get her son on the diet and only then due to new clinical trials at GOSH.

However, the parents of three-year-old Fionn say that they may have been too sceptical to try the diet if they hadn't tried the drugs first and found them lacking.

Iris and Robert Aherne from Westmeath first knew there was something wrong with Fionn when he was three months old.

"He would startle," Robert says, "as if shocked. We called them 'little frights' and took him to the doctor, who couldn't find anything wrong.

"Fionn was doing this several times a day but not in the doctor's surgery, so we decided to video it happening. The doctor immediately admitted Fionn to Our Lady's Children's Hospital, Crumlin."

The neurosurgeon, Dr Webb, diagnosed infantile spasms connected to epilepsy and prescribed steroids and Epilim. This helped the seizures but caused Fionn to puff out.

Robert says: "He was three times his normal size and he became like a vegetable. His development stopped and he didn't respond to us -- even when being injected with medicine."

Robert is unhappy about the medication and says they all had side effects, causing lethargy, mood changes or delayed development, yet none stopped the seizures. They then found out about the diet and asked their consultant to start them on it.

"Once he started the diet, it was amazing for us to be able to see him being a normal little boy who could smile and interact. He responded to what was going on around him and his seizures went down from around 30 a day to between none and four."

However, it doesn't work for everyone. Colette Daly from Dublin found the diet made her eight-year-old son Sean unwell. She says: "After two years of medication we decided to give the diet a try. But Sean produced too many ketones, and he often had tummy ache and diarrhoea.

"We tried for six months but there was no real improvement in Sean's condition."

Colette says that one of the problems with the diet is that it's a huge responsibility for the parents, who must become experts.

Because of her experiences, Colette is reluctant to try Sean on it again soon.

- Sarah Spendiff