But Associate Professor Stephen Shumak, of the Australasian College of Dermatologists, said there was no evidence that sunscreen absorption had any adverse effects on the participants.
"This is a small and preliminary study, involving 24 people, used to inform the design of future clinical trials investigating sunscreen systemic absorption," he said.
"The study subjects remained out of the sun, and thus there was no sun degradation of the sunscreen chemicals as is usual in normal day to day usage of sunscreens."
Professor Shumak said the study's participants applied far more sunscreen than a person usually would.
"The study used very large amounts of sunscreen applied to 75 per cent of the whole body four times a day for four days," he said.
"The authors of the study themselves state that further studies are needed to determine what this preliminary finding means in the health of Australians who rely on sunscreen as an effective way of protecting against the sun."
The study's researchers also emphasised the results did not mean people should stop using sunscreen to protect themselves from the sun's harmful ultraviolet rays.
"The demonstration of systemic absorption well above the Food and Drug Administration guideline does not mean these ingredients are unsafe," the study states.
"The study findings raise many important questions about sunscreen and the process by which the sunscreen industry, clinicians, specialty organisations, and regulatory agencies evaluate the benefits and risks of this topical over-the-counter medication."
David Andrews, a senior scientist at the nonprofit health and environmental advocacy group Environmental Working Group, said the study showed more thorough testing of sunscreen ingredients was required.
"For years, the sunscreen chemical manufacturers have resisted common sense safety testing for their ingredients and now FDA is proposing that these common ingredients must undergo additional testing to stay on the market," he said.
However, the Personal Care Products Council trade association pointed out the limitations of the study and expressed concern that it may confuse consumers.
Sunscreens in the study were used at "twice the amount that would be applied in what the scientific community considers real-world conditions," Alexandra Kowcz, the group's chief scientist, said.