Breastfed Infants With Food Allergy Show Lower Weight-for-Length at Five Months

Infants who were exclusively breastfed and carried a clinical diagnosis of food allergy had lower estimated weight-for-length Z-scores around five months of age than exclusively breastfed infants without food allergy, according to a prospective longitudinal cohort study conducted at the Children’s Hospital of Chongqing Medical University in China. The study, published in Frontiers in Nutrition, enrolled 73 infants at four to six months of age and followed them through infancy, with 268 anthropometric observations included in the longitudinal analysis.

The research team, led by first author Jun Fang with correspondence from Xuan Zhang, compared 30 infants with clinically diagnosed food allergy against 43 infants without food allergy. All participants were exclusively breastfed at enrollment. The investigators calculated three growth indicators according to the World Health Organization Child Growth Standards: weight-for-length Z-score (WLZ), weight-for-age Z-score (WAZ), and length-for-age Z-score (LAZ). The reported longitudinal results centered on WLZ.

The authors frame the study against a gap in the literature: food allergy in infancy may be accompanied by feeding difficulties and by dietary modifications during breastfeeding, which may influence early growth, yet longitudinal growth patterns in exclusively breastfed infants with clinically diagnosed food allergy remain incompletely characterized. The cohort was assembled to track growth through infancy rather than at a single visit.

To characterize growth over time, the researchers used linear mixed-effects models with infant-specific random intercepts, with age modeled continuously and centered at five months. The models estimated whether the two groups differed in average growth level and, separately, whether their linear rates of change differed over the follow-up period.

The results showed a difference in estimated weight-for-length around the midpoint of enrollment. In the longitudinal WLZ model, the estimated difference between the non-food-allergy and food-allergy groups at five months was 0.423 Z-score units, with a 95 percent confidence interval of 0.036 to 0.811 and a p-value of 0.035. Infants with food allergy had the lower estimated WLZ.

The analysis found no evidence of a group-by-age interaction. The interaction estimate was −0.011, with a 95 percent confidence interval spanning −0.086 to 0.063 and a p-value of 0.763. According to the authors, this indicates no detectable difference in the linear rate of WLZ change between the two groups over time.

Sensitivity analyses examined whether growth followed a nonlinear trajectory and whether the pattern differed between boys and girls. These analyses did not support a nonlinear WLZ trajectory, and no group-by-sex interaction was detected. The conclusions therefore emphasize a difference in estimated level near five months rather than a difference in the linear rate of change over infancy.

Maternal dietary avoidance was substantially more common among mothers of infants with food allergy than among mothers of infants without food allergy: 83.3 percent versus 18.6 percent, a difference the authors reported as statistically significant with p < 0.001. The abstract presents this contrast as one of the study’s key results.

The authors conclude that infants with clinically diagnosed food allergy had lower estimated WLZ around five months of age than infants without food allergy, but that the longitudinal analysis did not provide evidence that WLZ changed at a different linear rate between groups over time. Maternal dietary avoidance was substantially more common among mothers of infants with food allergy, and the authors underscore the importance of appropriate nutritional counseling and growth monitoring in this population.

The study was received by the journal on 01 July 2026 and accepted on 05 October 2026, and is published open access under the Creative Commons Attribution License. Within its scope — 73 exclusively breastfed infants enrolled at four to six months of age and followed through infancy — the study provides longitudinal estimates of both growth level and linear growth rate in a population the authors note had been incompletely characterized.

Subject of Research: Growth trajectories in exclusively breastfed infants with clinically diagnosed food allergy

Article Title: Growth trajectories in exclusively breastfed infants with clinically diagnosed food allergy: a prospective longitudinal cohort study

Article References: Fang, J., Zhang, Z., Zhong, Y., Wan, Y., Chen, Q., Xia, X., & Zhang, X. (2026). Growth trajectories in exclusively breastfed infants with clinically diagnosed food allergy: a prospective longitudinal cohort study. Frontiers in Nutrition, 13, Article 1924841. https://doi.org/10.3389/fnut.2026.1924841

Image Credits: AI Generated

DOI: 10.3389/fnut.2026.1924841

Keywords: food allergy, breastfeeding, infant growth, weight-for-length, maternal dietary avoidance, longitudinal cohort study, Growth, trajectories, exclusively, breastfed, infants, clinically