Background Liquid laundry capsules have been involved in child poisoning incidents, allegedly due to product appearances. This research explored potential influence of capsule size on toddler interaction.

Methods We compared two capsule designs identical in appearance but different in size through three studies: (a) forced-choice test in laboratory setting; (b) simulated real-world setting of laundry cabinet with open container of capsules; and (c) simulated real-world cabinet with capsule outside its container. Capsule interaction was measured by grasping choice among samples of 156 toddlers ages 9–36 months in each study.

Results Study 1: Toddlers selected the small (49.8% selection) and large (50.2%) capsule with nearly identical frequency. Study 2: Toddlers grasped the small (26.8%) and large (22.3%) capsule or container of capsules with similar frequency. Study 3: Toddlers grasped the small (18.0%) and large (19.2%) capsules with similar frequency. No consistent gender or age differences existed. Study 1 found toddlers selected capsules closest to their dominant hand more frequently, no matter their size.

Conclusion Findings consistently failed to demonstrate statistical differences in toddler interaction with different-sized capsules. We conclude the difference in size (small vs large capsules) is not expected to impact toddler interaction rates in the home.

Learning Outcomes Extending previous research concerning laundry capsule colours, size also seems unlikely to impact child poisoning risk. The work offers valuable evidence for action to reduce child poisoning incidents, supporting current strategies to reduce risk through theory-driven caregiver education and use of packaging with barriers to prevent young children’s access to capsules.