Models, influencers… chemists?

Last month, model and influencer Nara Smith said she recently ran out of sunscreen. Instead of buying more, she asked her husband, Lucky Blue Smith, to make her own.

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

In a certain part of social media, Ms. Smith has become known for this kind of DIY content. It started with posting recipes to satisfy food cravings, but grew to include videos of her husband making personal care products like sunscreen, toothpaste and moisturizer from scratch.

Some commentators admire the couple’s homemade cosmetics, while others question whether the content is satire. But cosmetic chemists, dentists and dermatologists agree that making beauty products from scratch isn’t always a good idea. Homemade moisturizer poses few risks, but homemade sunscreen offers far less protection, and homemade toothpaste can be bad for tooth enamel, experts say.

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

Cosmetic chemistry isn’t like baking, said Marisa Plescia, vice president of the Society of Cosmetic Chemists. Experts create products according to precise formulas; trying to do that process at home if you’re not a chemist can result in DIY products that aren’t effective, don’t last long or react badly with your skin, she said.

“Baking? You can follow a recipe that you can find online or on the back of the box,” Ms. Plescia said. “Cosmetics? Yes, it’s a recipe, but it’s much harder to follow.”

Homemade sunscreen

Mrs. Smith’s Sunscreen TikTok video has now been viewed more than 19 million times.

Cosmetic chemists in the United States must meet Food and Drug Administration requirements to determine which active ingredients in sunscreen are safe and whether they can be combined, Ms. Plescia said.

Making your own sunscreen is a challenge because the formulas are precise: zinc oxide, for example, is considered safe to use in sunscreen, but it may not constitute more than 25 percent of a mixture.

Chemists also test sunscreen to make sure it has the sun protection factor (SPF) stated on the label and that the ingredients remain effective over the shelf life of the sunscreen.

Under most circumstances, homemade sunscreen provides weak and patchy protection, and it can quickly lose its effectiveness, experts said. Using ineffective homemade sunscreen exposes you to ultraviolet radiation, which increases your risk of skin cancer and accelerates the chances of skin cancer developing. signs of agingsuch as wrinkles and pigment spots, says Dr. Brooke Jeffy, a board-certified dermatologist in Scottsdale, Arizona.

“You are literally putting yourself in danger,” Ms. Plescia said.

TikTok Toothpaste

The Smiths’ toothpaste The video has been viewed over 38 million times. In it, the couple makes toothpaste with bentonite clay (a gray powder made from montmorillonite and other minerals that is used as a natural remedy), water, coconut oil, baking soda, stevia, and peppermint oil.

Dr. Purnima Kumar, chief of the department of periodontology and oral medicine at the University of Michigan, said she doubts the feasibility of homemade toothpaste because it’s difficult to know whether the ingredients are too abrasive or contain harsh chemicals that could erode enamel, the outer layer of the tooth that protects against cavities.

Many ingredients used in homemade toothpaste, such as bentonite clay, have not been studied for their safety for enamel, Dr. Kumar said.

Glaze cannot be replaced According to Dr. Kumar, if it is damaged and worn down, your teeth are more likely to rot or become sensitive.

So when it comes to using homemade toothpaste, “one has to consider whether this is a risk worth taking,” Dr. Kumar said.

Mixing moisturizer

When Mr. Smith ran out of store-bought moisturizer, he made his own video which has now been viewed over 28 million times. For this he used beeswax, squalene, jojoba oil, hyaluronic acid, glycerin, vitamin E oil and beef suet.

“If you do want to stick more to home recipes, using vegetable oils is a great option,” Ms. Plescia said, adding that “there are people who make their own moisturizers all the time.”

Jojoba oil and squalene are vegetable oils and emollientswhich means they hydrate and soften the skin by strengthening its natural barrier and forming a layer that prevents moisture from escaping; beef suet is also considered an emollient. Hyaluronic acid and glycerin are wetting agentswhich hydrate by attracting and holding the water molecules in your skin. Beeswax has both humectant and emollient properties, while vitamin E is an antioxidant that is frequently used in skin care products because it is hydrating and helps protect the skin from damage.

It’s difficult to know how long a homemade cosmetic will remain effective before it goes rancid without proper testing, Ms. Plescia said, but the ingredients in the Smiths’ homemade moisturizer are relatively harmless. Some of them, she added, “have been used for skin care for thousands of years.”