Objectives: To measure the thickness at which primary schoolchildren apply sunscreen on school day mornings and to compare it with the thickness (2.00 mg/cm²) at which sunscreen is tested during product development, as well as to investigate how application thickness was influenced by age of the child (school grades 1-7) and by dispenser type (500-mL pump, 125-mL squeeze bottle, or 50-mL roll-on).

Design: A crossover quasiexperimental study design comparing 3 sunscreen dispenser types.

Setting: Children aged 5 to 12 years from public primary schools (grades 1-7) in Queensland, Australia.

Participants: Children (n = 87) and their parents randomly recruited from the enrollment lists of 7 primary schools. Each child provided up to 3 observations (n = 258).

Intervention: Children applied sunscreen during 3 consecutive school weeks (Monday through Friday) for the first application of the day using a different dispenser each week.

Main Outcome Measure: Thickness of sunscreen application (in milligrams per square centimeter). The dispensers were weighed before and after use to calculate the weight of sunscreen applied. This was divided by the coverage area of application (in square centimeters), which was calculated by multiplying the children's body surface area by the percentage of the body covered with sunscreen.

Results: Children applied their sunscreen at a median thickness of 0.48 mg/cm². Children applied significantly more sunscreen when using the pump (0.75 mg/cm²) and the squeeze bottle (0.57 mg/cm²) compared with the roll-on (0.22 mg/cm²) (P < .001 for both).

Conclusions: Regardless of age, primary schoolchildren apply sunscreen at substantially less than 1.00 mg/cm², similar to what has been observed among adults. Some sunscreen dispensers seem to facilitate thicker application than others.