Run cold water first then add hot water for infant baths, test water on your inner wrist or elbow before placing the child, and set water heaters below 50 °C (120 °F)

Hot tap water at 65 °C (150 °F) causes third-degree full-thickness burns on adult skin in just 2 seconds; infant skin is significantly thinner and burns much faster and deeper. Always run cold water into the tub first, mix in hot water thoroughly, and verify with your inner wrist or elbow before bathing. Never bathe an infant under running tap water. When Washington State required water heaters to be preset to 49 °C (120 °F), pediatric tap water burn hospitalizations dropped by more than half.

Free. Takes 1–2 minutes per bath to test water temperature. A floating bath thermometer is optional. The friction is maintaining the habit when tired, rushed, or when the baby is crying.

The U.S. Consumer Product Safety Commission (CPSC) reports that water at 150 °F (65 °C) causes full-thickness third-degree scalds in adults in 2 seconds; 140 °F (60 °C) causes scalds in 6 seconds; 130 °F (54 °C) in 30 seconds; and 120 °F (49 °C) requires prolonged exposure (5 minutes). World Health Organization and UNICEF reports emphasize that infant epidermis and dermis are markedly thinner than adults, causing deeper, more extensive burns at lower temperatures and shorter contact times. The AAP cautions parents to always test bath water with the sensitive skin of the inner wrist or elbow, aiming for comfortably warm rather than hot, and strictly warns never to bathe an infant under running tap water where sudden pressure fluctuations cause rapid temperature spikes. Washington State enacted legislation in 1983 requiring new residential water heaters to be preset at 49 °C (120 °F); by 1988, mean domestic hot water temperatures dropped from 61 °C to 50 °C, and pediatric tap scald hospitalizations plummeted from 5.5 per year to 2.4 per year, with significant reductions in burn surface area, skin grafting, and mortality. In Australia, New South Wales mandated a 50 °C maximum delivery temperature for bathroom taps, resulting in a 13% decline in burn hospitalizations among children aged 0–4 and a 30% decline in severe scalds requiring more than 10 days of hospitalization. Retrospective analyses across Chinese pediatric burn centers show hot liquids account for 87.6% to 90.6% of hospitalized burns, with children under 3 years at peak vulnerability.

Graded B because findings derive from legislative before-and-after studies and burn center epidemiological registries rather than controlled trials. For tankless (on-demand gas) water heaters, set the master outlet temperature directly to 48–50 °C (120 °F). For electric storage water heaters, WHO Legionella guidance recommends maintaining tank water at 60 °C (to inhibit Legionella pneumophila bacteria) while installing thermostatic mixing valves at bathroom outlets to limit delivery temperature to 50 °C. Never leave an infant unattended in the bath for any reason (over half of infant tub drownings occur in moments of inattention; see Chapter 1, Rule 12). Avoid holding an infant while carrying hot coffee or tea, which represents the most frequent scald mechanism in high-income countries. For immediate burn first aid, flush with cool tap water (see Chapter 13, Rule 14).

US Consumer Product Safety Commission. Avoiding Tap Water Scalds (Document 5098). https://www.cpsc.gov/s3fs-public/5098.pdf；American Academy of Pediatrics (2025). Bathing Your Baby. HealthyChildren.org. https://www.healthychildren.org/English/ages-stages/baby/bathing-skin-care/Pages/Bathing-Your-Newborn.aspx；NHS. Washing and bathing your baby（2024-07-23 审阅）. https://www.nhs.uk/baby/caring-for-a-newborn/washing-and-bathing-your-baby/；World Health Organization, UNICEF (2008). World report on child injury prevention, Chapter 4 Burns（同一页有中文版《世界预防儿童伤害报告》）. https://iris.who.int/handle/10665/43851；Erdmann TC, Feldman KW, Rivara FP, Heimbach DM, Wall HA (1991). Tap water burn prevention: the effect of legislation. Pediatrics, 88(3), 572-577. https://europepmc.org/article/MED/1881739；Xu JH, Qiu J, Zhou JH, et al. (2014). Pediatric burns in military hospitals of China from 2001 to 2007: a retrospective study. Burns, 40(8), 1780-1788. https://doi.org/10.1016/j.burns.2014.04.003；Zhu L, Zhang Y, Liu L, et al. (2013). Hospitalized pediatric burns in North China: a 10-year epidemiologic review. Burns, 39(5), 1004-1011. https://doi.org/10.1016/j.burns.2012.12.014；Han D, Wei Y, Li Y, et al. (2022). Epidemiological and Clinical Characteristics of 5,569 Pediatric Burns in Central China From 2013 to 2019. Frontiers in Public Health, 10, 751615. https://doi.org/10.3389/fpubh.2022.751615；World Health Organization (2007). Legionella and the prevention of legionellosis. https://iris.who.int/handle/10665/43233