Consumers also expressed frustration on the product's Amazon page, saying it didn't prevent burning "at all" and "honestly doesn't work."
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The Honest Company issued a statement Friday regarding the complaints, saying it stands by the "safety and efficacy" of the sunscreen lotion.
They also said the product meets the standards issued by the U.S. Food and Drug Administration when used as directed, which includes applying 15 minutes before sun exposure and reapplying after 80 minutes of swimming or sweating.
The company also said the product was tested by an independent third party, per FDA protocol.
The FDA requires sunscreen products to use up to 25% of zinc oxide. An investigation by NBC Chicago found the Honest Company dropped the percentage of the ingredient from 20% to 9.3% at some point.
The investigation also detailed the story of Gretta Stabler from Naperville, Ill., who used the product on her 6-year-old daughter while at the pool. Stabler told NBC Chicago she applied the sunscreen four times over a three-hour period.
"She got really burned on her arms, shoulders, legs face, pretty much everywhere. I was angry," Stabler told NBC Chicago.