Doctors have discovered a child's risk of developing an allergic disease is doubled if a parent of the same sex has suffered from it, new research has claimed.
Professor Hasan Arshad, a consultant in allergy and immunology at Southampton General Hospital, found that allergies such as asthma and eczema were gender-related and not simply hereditary.
"We have known for decades that allergy runs in the family and many thought that maternal effect was greater than paternal effect due to a mothers' closeness to her child, but we have discovered the inheritance is from mother to daughter and father to son," Prof Arshad said.
His team assessed 1,456 patients recruited from birth 23 years ago and found the risk of asthma in boys was only increased if their fathers suffered from the condition while, if mothers had asthma, it doubled the risk in their daughters but not sons.
The research, published in the Journal of Allergy and Clinical Immunology and funded by the National Institute of Health in the US, also showed maternal eczema led to a 50% increased risk of eczema in girls, while paternal eczema did the same for boys.
"In the past, studies looking at the effect of parental allergy on children have not split their samples according to the sex of the child, having assumed the mother and father influence is identical in males and females," explained Prof Arshad, who is also chair of allergy and immunology at the University of Southampton.
"Now, with these groundbreaking findings, we should see a change in the way we assess a child's risk of disease, asking girls for the allergy history of their mother and boys for that of their father.
"This work also opens up novel areas for further research in the genetics of allergy as to why this sex dependent effect occurs and, if we can find the reason, we can try to find a way of preventing sex-specific disease," he added.
Bevis Man, from the British Skin Foundation charity, welcomed the research.
"This news is very interesting and sheds light on how eczema from parents can ultimately affect their children," he said.
"There has been a great deal of research over the past 10 years focusing on the genetics of eczema and the genetic defects that may lead to the development of eczema.
"This news will hopefully spur a new wave of research looking into the differences between the sexes and the role in which a child is likely to develop the disease.
"Although a large proportion of children will simply 'grow out' of eczema, for many adults, this is not the case, so any new developments in understanding the disease are most welcome."
Leanne Metcalf, assistant director of research and practice at Asthma UK, said: "Scientists established a long time ago that asthma is caused by genetic and environmental factors interacting; who you are, what you do and what you are exposed to will all influence your risk of getting asthma.
"However we don't fully understand how all these factors, including gender, come together to cause asthma.
"This study is exciting because it opens up interesting new avenues of research that could tell us more about the relative role of genes, environment and gender in terms of asthma risk, and enable us use this information to potentially prevent asthma in the future."