T07028: The influence of dose and route of exposure on the early life origins of peanut allergy

Study Duration: July 2001 to March 2004

Contractor: University of Southampton

The Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) issued advice in 1998 recommending that women with a first degree relative with an allergy should avoid peanuts and peanut products during pregnancy and breastfeeding. The Committee also advised that children of these women should not be given such foods until 3 years of age.

However, recent research suggests that avoidance may not the best strategy in preventing food allergy, and complete avoidance is extremely difficult to achieve.

The researchers will develop a sensitive enzyme-linked immunosorbent assay (ELISA) technique, which will be used to screen maternal, paternal and infant sera and breast milk for peanut allergen and a range of antibodies.

The researchers will use diet diaries kept by pregnant women who have either been diagnosed or whose partner has been diagnosed as being atopic. Peanut avoidance advice is given before women are recruited to the study by midwives and/or health visitors, and again by the study dietician at recruitment. In addition, a questionnaire detailing peanut consumption during pregnancy will be administered retrospectively to other atopic women or those with atopic partners.

Maternal biological samples have previously been screened for levels of peanut-specific IgG, using an optimised and validated 'in-house' assay. Peanut-specific IgG was measured in maternal sera samples. Breast milk samples have also been screened for peanut-specific IgG; this data is currently being statistically analysed.

The aims of this project were to:

• Establish whether avoidance of peanut and peanut products during pregnancy and breastfeeding does or does not have any effect on the subsequent development of peanut allergy in children.
• Establish the doses and routes of exposure to peanut proteins.
• Establish whether any characteristics of the mother�s and newborn�s immune response to peanut proteins is associated with the development of peanut allergy.

Dietary analysis in the study has shown that despite being given advice on avoiding peanut, many pregnant women found this impossible to do. The immunological analysis has failed to identify any links between maternal intake of peanut and either a causative or protective effect, with regards the development of peanut allergy, as measured in the first 18 months of life. The possibility of a correlation between allergen exposure, antibody production and clinical outcome can not be excluded. However, it is unlikely that there is a linear relationship between exposure dose and risk of sensitisation to peanut. Observations to date suggest that the recommendation of the Committee on Toxicity of Chemicals & Foods may not have any impact on peanut sensitisation rates. Before drawing any final conclusions, however, it will be necessary to follow the cohort to mid-childhood to establish which children develop clinical peanut allergy rather than just peanut sensitisation. It is most important to draw a distinction between these two phenomena. Evidence is accruing that sensitisation can occur on exposure to incredibly low doses of allergen, particularly if this is in early life. However, there is good evidence that there is a linear relationship between dose of allergen exposure and the risk of developing allergic disease. Thus there is still a potential that the recommendation will have an impact on clinical manifestations of peanut allergy. The main difficulty in establishing whether this is the case is the statistical power of studies. As peanut allergy affects around 1-2% (most recent data) of children, a much larger cohort is needed.

The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: library&info@foodstandards.gsi.gov.uk)

Contact: For any enquiries concerning this research project, please contact the relevant Programme contact or email food.allergy@foodstandards.gsi.gov.uk