Sunscreen sold by actress Jessica Alba's Honest Company, which makes eco-friendly household, baby and personal care products, is under fire from disgruntled consumers who claim the product doesn't work. Across social media, customers are posting photos of their scorched skin, claiming they got burned while using Honest Sunscreen Lotion. 

The lotion, which has an SPF of 30, is mineral based. According to the Mayo Clinic, mineral-based sunscreens, also called physical sunscreens, rely on zinc oxide or titanium dioxide to reflect and scatter UV radiation. 

"I recommend physical sunscreens because they provide the best protection," adds Heather D. Rogers, MD, a board-certified dermatologist in Seattle, Washington. "Zinc provides the widest range of protection, from the longest wavelength of UVA to the shortest wavelength of UVB."

Related: Are Your Sunscreen Ingredients Safe?

An honest defense

If zinc-based sunscreens are the most effective under the sun, why does Honest Sunscreen Lotion seem to be falling down on the job? It may be it contains less zinc oxide than similar sunscreens. According to an NBC investigation, the company's sunscreen contains 9.3 percent. Other sunscreens contain between 18 and 25 percent zinc oxide. 

Rogers wonders if one reason people are getting sunburned while using Honest Company Sunscreen is they aren't reapplying it as often as is recommended for any type of sunscreen — every two hours — or slathering it on thickly enough. Most people apply just 25 to 50 percent of the recommended amount of sunscreen, according to American Academy of Dermatologists. "Zinc-based sunscreens can make you feel white, chalky or sticky," she says. "Some are really thick. The Honest one falls into that group." Many of those who've complained about the sunscreen say they got burned despite regularly reapplying it.  

In response to the outrage by users of its sunscreen, the Honest Company has released a statement saying that it stands behind its product and it meets Food and Drug Administration (FDA) standards. Although the FDA doesn't test products, it requires manufacturers to do so. The Honest Company says its sunscreen was tested by an independent third party.

Related: 6 Places You're Forgetting to Put Sunscreen

How to go natural

When choosing a natural sunscreen — that is, one that physically blocks sun rays rather than relies on chemicals to protect skin — the key is to find one that feels good and doesn't irritate skin so you don't mind reapplying it, advises Rogers.

It's also important to read labels for specific ingredients and other features. 

SPF 30. The American Academy of Dermatologists recommends using a sunscreen with an SPF of 30 or higher. Keep in mind, though, that most people don't use as much sunscreen in real life as scientists do when testing it. In fact, most folks use about half as much, which reduces sun protection to around SPF 15. Rogers suggests using a shot glass worth of sunscreen on your body and about a teaspoon for your face. 

Zinc content. Find a sunscreen that's at least 5 percent zinc, says Rogers. (Which suggests the 9.3 percent in Honest Company Sunscreen lotion should be plenty.)

Broad spectrum. This means the product will protect skin from UVA rays as well as UVB rays. "We now know that UVA plays an important role in aging and skin cancer," Rogers explains. 

Water-resistant. This won't be necessary for a sunscreen you plan to use under make up at work. "But if you'll be wearing it all day at the beach or pool, you'll want a product labeled water-resistant," says Rogers. "After you've been in the water for eighty minutes you should get out, towel off and reapply it." (Note that sunscreens no longer can claim to be "waterproof.")

Related: Beyond Sunscreen: Other Bright Ways to Protect Your Skin

Muriel Vega is a writer with a passion for budget travel and staying safe while abroad. A Georgia State University graduate, she has over 6 years of editorial experience and has written for The Guardian, The Atlantic, The Billfold, among other outlets. In her free time, you can find her baking pies, playing with her two dogs and cat, or planning her next vacation. She spends way too much time on Twitter, one of her favorite social media channels. Her favorite safety tip: Make sure you have all the necessary shots before you go abroad.