Jessica Alba's billion dollar start-up, The Honest Company, is known for its organic and "safe" baby and household products.

But furious parents are saying the company's sunscreen doesn't work.

Chicago mother Gretta Stabler purchased The Honest Company's SPF 30 sunscreen at Costco, according to the local NBC affiliate. During a recent trip to the pool, she applied sunscreen to her 6-year-old daughter Maggie four times, Stabler claims.

"She got really burned on her arms, shoulders, legs face, pretty much everywhere. I was angry," Stabler said.

The Food and Drug Administration told NBC that companies are responsible for testing the effectiveness of their own products. The company says the product was tested by an independent third party, and is safe when its used properly, NBC reported.

The Honest Company recently reduced the amount of zinc, an ingredient that protects skin from the sun, according to NBC. The company says it added other ingredients instead.

Amazon reviews for the sunscreen are largely negative. About 57% of the 135 people who reviewed the product gave it one star.

Gretta Stabler claims her daughter, Maggie, got a sunburn after using The Honest Company's sunscreen. NBC 5

"I've tried dozens of different sunscreens and words can't come close to describing how terrible this product compares even to the cheapest stuff you find at discount stores," one customer writes on Amazon. "First, the product applies like a layer of grease — imagine putting melted butter on your skin. Next, the grease doesn't wash off, even with vigorous scrubbing and multiple hand washes. Last, and most importantly, the sun protection from this product is about as good as no sunscreen. I was in the sun for less than an hour and my whole family was burnt."

Other customers complained of burns and blisters.

Other parents on Amazon gave the product positive reviews.

"This is the only sunblock we use on our daughter...I actually like that it's a little greasy when you first rub it in, her skin is dry and just soaks it up," one customer writes.

The Honest Company provided this statement to Business Insider:

"The Honest Company is committed to providing safe and effective products, and we take all consumer feedback very seriously. Our Sunscreen Lotion was tested, by an independent 3rd party, against the protocols prescribed by the U.S. Food & Drug Administration's (FDA) monograph for over-the-counter sunscreen products. The results showed that our product is effective and safe for use as an 80 minute water-resistant (FDA's highest rating), SPF 30 sunscreen lotion in accordance with FDA regulations when used as directed (Shake Well. Apply liberally and evenly 15 minutes before sun exposure. Reapply after 80 minutes of swimming or sweating, immediately after towel drying and at least every 2 hours). The number of complaints received on our own website about our Sunscreen Lotion constitute less than one half of one percent of all units actually sold at honest.com. We stand behind the safety and efficacy of this product. "