Nara Smith’s Homemade Sunscreen Gives Experts Pause

Last month, the model and influencer Nara Smith said she had recently run out of sunscreen. Instead of buying more, she asked her husband, Lucky Blue Smith, to make some from scratch.

Mr. Smith’s process, which Ms. Smith posted to TikTok last month, looked more like a cooking video than anything else. Wearing an unbuttoned shirt and holding a toothpick between his lips, he combined ingredients including coconut oil, shea butter, jojoba oil and zinc oxide powder in a clear bowl.

In a certain pocket of social media, Ms. Smith has become known for such do-it-yourself content. It began with her posting recipes to satisfy food cravings, but grew to include videos of her husband making personal care products such as sunscreen, toothpaste and moisturizer from scratch.

Some commenters admire the couple’s D.I.Y. cosmetics, while others wonder whether their content is satire. But cosmetic chemists, dentists and dermatologists agree that making beauty products from scratch isn’t always a good idea. Homemade moisturizer presents few risks, but homemade sunscreen is far less likely to offer protection, and D.I.Y. toothpaste may be bad for tooth enamel, experts said.

Ms. Smith, who did not respond to requests for comment, has at times nodded to the limitations of her experience. In the toothpaste video, for example, she acknowledged that she is not a professional dentist. But at other times, as in her sunscreen TikTok, she assured viewers that her husband “is a baker, so he makes sure that everything is very precise.”

Cosmetic chemistry is not the same as baking, said Marisa Plescia, the vice president-elect of the Society of Cosmetic Chemists. Experts make products according to precise formulas; attempting that process at home when you’re not a chemist can lead to D.I.Y. products that are ineffective, don’t last long or react poorly with your skin, she said.