London - Years of advice to avoid giving babies peanuts could be ditched as experts backed feeding them to infants as soon as they are weaned.
In a U-turn, scientists said there was a broad consensus that parents should be told "not to delay" introducing the food.
It is thought the move could stem an epidemic of potentially fatal allergies and comes as new US guidance urges parents to give diluted peanut butter to babies as young as four months.
Mothers and fathers used to be told not to give peanuts to children with a family history of a peanut allergy until they were at least three – and to all others until they were at least one.
That guidance was scrapped in 2009, when they were told to avoid peanuts until their babies were at least six months, irrespective of allergies.
But officials in the US changed tack by announcing the most at-risk children should be given peanuts as early as four months – although they should be tested for allergies first.
But mounting evidence suggests giving peanuts to infants slashes the odds of developing an allergy.
Peanut allergy develops early in life, is rarely outgrown and there is no cure. At its most dangerous, it may cause anaphylactic shock, which can be fatal.
The US National Institutes of Health said that babies who already had eczema or an egg allergy – strong signs they might be at risk of a peanut allergy – should be given peanut butter dissolved in water from four months. Babies who do not have the warning signs should be given peanut products "freely" when they start on solid food.
The guidance, based on a studies led by British scientists, says those at risk should have a test to make sure they are have not developed an allergy, and then be fed peanuts – in the presence of a doctor on the first occasion.
Dr Stephen Tilles, of the American College of Allergy, Asthma and Immunology, said: "This update offers a lot of promise.
"Peanut allergy has become an epidemic, and now we have a clear roadmap to prevent many new cases."
He praised the Learning Early About Peanut allergy study (Leap) – led by King’s College London and Southampton University – as having "paved the way for the updated guidelines", adding: "I cannot think of a single publication with more of an impact."
That study found that if babies were fed peanut butter in their first year of life, they were 74 percent less likely to have developed a peanut allergy by the time they were six. A separate review, published in September by Imperial College London, found feeding peanut butter to babies between four and 11 months could cut the risk of an allergy by 70 percent.
Professor Alastair Sutcliffe, a paediatrician at University College London, said: "Due to potentially catastrophic but rare deaths there has been immense public concern regarding nut allergies.
"What the Leap studies have shown – and in fact reversed conventional wisdom – is if peanuts are introduced very early the risk of developing the allergy is substantially reduced. This is in a sense the opposite of previous practice."