This French multicenter, cross-sectional, observational study aimed to describe the family history of atopy in infants with cow's milk protein allergy (CMPA), and the related diagnostic approaches used by specialists in a real-life ambulatory setting.

In total, 1674 infants with suspected CMPA [median age 4.5 months (range: 0.1–18.0), males 54%] were enrolled in the study by 466 private physicians (pediatricians: 97%). Family history of atopy was defined as a known history of atopy in at least one first- (father, mother, and/or sibling) and/or second-degree relative (grandparents, uncles, and aunts), as reported by parents to physicians.

Atopy in a first-degree relative was more common among infants with documented or high probability of CMPA (in 84% and 80% of cases, respectively, vs. the other subgroups, P=0.005). Most infants experienced digestive (92%) and skin (61%) symptoms suggestive of CMPA. Delayed reactions were reported in 64% of infants. According to a post-classification based on the results of previous diagnostic tests and procedures, 1133 infants (68%) had highly probable (52%) or documented CMPA (16%). In these infants, a history of atopy was reported in first- and/or second-degree relative(s) in 86% of cases (81% in first-degree relatives). Whatever the family history of atopy, the characteristics of the infants were similar, except for fewer pets in the case of negative family atopy (14% vs. 25%, P<0.001). Atopy in a parent was more frequent in infants who presented with the first signs suggestive of CMPA within the first 6 months of life vs. those with later first symptoms (75% vs. 65%, P=0.063).

This French study confirms the high rate of family history of atopy in first-degree relatives of infants with probable or documented CMPA.