21In 2016, the US Food and Drug Administration banned the use of specific microbicides 22 in some household and personal wash products. This decision was due to concerns that these 23 chemicals might induce antibiotic resistance or disrupt human microbial communities. Triclosan 24 and triclocarban (referred to as TCs) are the most common antimicrobials in household and 25 personal care products, but the extent to which TC exposure perturbs microbial communities in 26 humans, particularly during infant development, was unknown. We conducted a randomized 27 intervention of TC-containing household and personal care products during the first year 28 following birth to characterize whether TC exposure from wash products perturbs microbial 29 communities in mothers and their infants. Longitudinal survey of the intestinal microbiota using 30 16S ribosomal RNA amplicon sequencing showed that TC exposure from wash products did not 31 induce global reconstruction of either infant or maternal intestinal microbiotas following 10 32 months of exposure after birth. However, broadly antibiotic-resistant species from the phylum 33 Proteobacteria were enriched in stool samples from mothers in TC households only after the 34 introduction of triclosan-containing toothpaste. Despite the minimal effects of TC exposure from 35