Background Parents of atopic children frequently report, and are alarmed by, contact reactions to foods. Some schools restrict foods due to concerns regarding possible systemic reactions following contact in allergic children.
Objective We aimed to determine the frequency with which peanut-sensitive children exhibited contact sensitivity to peanut butter and to assess the significance of such reactions.
Methods One gram of peanut butter was applied directly to the skin of 281 children who were skin prick test (SPT) positive to peanut (immediate skin application food test; I-SAFT). The test was considered positive if one or more weals were present when the patch was removed after 15 min. A subset of children then underwent an open-label oral challenge with graded amounts of peanut protein.
Results During 3515 clinic visits, 330 I-SAFT tests for peanut contact sensitivity were performed; 136 (41%) were positive. The mean SPT diameter was 10 mm in the I-SAFT-positive children and 8.5 mm in the I-SAFT-negative children (t-test, P<0.0001). No child had a systemic reaction following topical application of peanut butter. Eighty-four children had 85 oral challenges after blinded, placebo-controlled I-SAFT testing. Challenge was positive in 26/32 of those with a positive I-SAFT and negative in only 6/32. Challenge was also positive in 26/53 but negative in 27/53 of those with a negative I-SAFT (sensitivity 50%, specificity 82%, χ2, P=0.003).
Conclusion A minority of children sensitized to peanut (positive SPT) develop localized urticaria from prolonged skin contact with peanut butter. No tested subjects, including ones with systemic reactions upon oral challenge, developed a systemic reaction to prolonged skin exposure to peanut. Therefore, systemic reactions resulting from this mode of contact with peanut butter appear highly unlikely.