Buyer beware

If beauty is in the eye of the beholder, then it’s no surprise that consumers are fueling the multibillion-dollar global skin care industry, helped along by social media and loose regulatory action. Dermatologists are watching these trends as well as the resulting wave of allergic skin reactions, and understandably, there is cause for concern.

That’s according to Houston dermatologist Megan Rogge, MD, FAAD, an associate professor of dermatology at the University of Texas McGovern Medical School. Increasing product exposures to the skin may translate to an uptick in allergic contact dermatitis (ACD) cases. Addressing a full range of practices and products, Dr. Rogge said the trends range from “natural” skin care ingredients to at-home manicure kits — some of which carry a risk of adverse events.

I saw it on TikTok

Megan Rogge, MD, FAADMany of these skin care trends are driven by social media influencers, she said, who spread unfounded claims of brighter or clearer skin. Trends that promote bioactive ingredients, such as retinol, salicylic acid, and vitamin C, have the highest reported risk of ACD, Dr. Rogge said, though irritation reactions are the most common. Most instances of ACD to cosmeceutical products are linked to inactive ingredients, such as fragrances or preservatives.

“Retinol, for example, is a popular ingredient featured in cosmeceuticals because it is a relatively stable compound with less irritation/better tolerability than retinoic acid,” she said.

However, irritant contact dermatitis (ICD) and the distinct retinoid dermatitis are common side effects, she added.

“Traditional irritant contact dermatitis is driven by innate immune activation following direct barrier disruption. Retinoid dermatitis has a unique pathway, leading to mast cell degranulation and stimulation of the TRPV1 neurogenic receptor in the skin, which results in burning, stinging, and itch,” Dr. Rogge said.

Salicylic acid, or lipophilic beta-hydroxy acid, is often used as an exfoliant to decrease sebum production, Dr. Rogge said. It’s associated with ICD, although ACD is likely more common than previously thought.

“The thinking is that dermatologists are missing this allergy because we aren’t testing for it on standard patch testing trays,” she said.

Vitamin C is also bioactive but is unstable; therefore, many derivatives are used in cosmeceuticals instead. When used as an antioxidant, vitamin C is commonly associated with irritation reactions, Dr. Rogge said. ACD has been reported from several of the vitamin C byproducts, but these reactions have “notably low cross reactivity with other vitamin C derivatives,” she said.

But it’s all natural

Conversely, natural ingredients don’t always mean a product is safe, Dr. Rogge said. In fact, she said there is often a misconception by patients and consumers that “natural” means without risk. “We know that plants and their derivatives can be harmful, as in the common case of allergic contact dermatitis to poison ivy.”

Ingredients such as castor oil, bakuchiol, and Centella asiatica — found in skin care products that are gaining popularity — have been identified as having allergic potential. As these products become more widely used, Dr. Rogge said dermatologists can expect to see a corresponding uptick in allergy cases.

Similarly, she said, botanicals used in skin care products may cross-react with existing fragrance allergies, putting some consumers at even greater risk. Fragrances in general are a problem, as they are among the most prevalent of allergies, she said. Several botanical extracts or essential oils share a similar terpene chemical structure and cross-react with fragrance more than 60% of the time, she said. The biggest offenders are lavender, tea tree, jasmine, ylang-ylang, peppermint, citrus/limonene, frankincense, and cypress.

“Roughly 10% of patch tests show allergy to fragrance and this remains a highly relevant allergen category (in the top five calculated SPIN),” Dr. Rogge said. “Essential oils, which are distilled portions of specific botanicals, have been repeatedly shown to contain fragrance allergens and, as such, have been firmly categorized as ‘fragrance’ by previous studies.”

The eyes have it

Cory A. Dunnick, MD, FAADCory A. Dunnick, MD, FAAD, a professor of dermatology at the University of Colorado Anschutz Medical Campus in Aurora, has been monitoring popular eyebrow and eyelash cosmetic trends. Eyelash and eyebrow products may contain chemicals that should be used with caution around the eyes, she said, as ACD is a common complication. The chemicals in question are commonly associated with trends such as eyebrow extensions, lamination, tinting, tattoo/henna, and microblading. Dr. Dunnick’s team reviewed 177 TikTok videos dedicated to eyelash trends and found that most products contain known allergens.

Prostaglandin serums are popular to promote growth of eyelash hair, Dr. Dunnick said, but unwanted side effects can include excess hair around the eyes, hyperpigmentation of eyelid skin, and eye irritation. Periorbital fat atrophy can induce a “medical blepharoplasty” but may cause eyes to appear more hollow or sunken, she said. Less common or potentially permanent side effects include a change in iris color.

Sticky situation

Acrylates are another commonly used ingredient found in popular nail beauty products like shellac, dip, and builder gel. Home manicure kits can elicit sensitization to acrylate allergens especially 2-hydroxyethyl methacrylate, Dr. Dunnick said.

Another rising health trend is to wear continuous glucose monitors not just for diabetes but as a health and wellness tool or training tool for elite athletes. These are designed to be worn for several days to months, and ACD may develop with prolonged use, said Dr. Dunnick. Risk factors include repetitive occlusion, maceration of the skin, and disrupted skin barrier.

“Many diabetic continuous glucose monitors use adhesives, such as isobornyl acrylate, ethyl cyanoacrylate, and acrylate polymers,” she said. “Other reported allergens in the device adhesives include sesquiterpene lactone, colophony, polyurethane, epoxy resin, and nickel.”

Color me allergic

According to Dr. Dunnick, shampoos contain surfactants, preservatives, and fragrances that may trigger ACD, presenting around the hairline, often sparing the scalp. ACD is also a common complication for those who dye their hair or tint their eyelashes, she said, as most permanent hair dyes contain paraphenylenediamine (PPD).

“Allergy to hair dyes can produce swelling, blistering, or scaling with swelling of the eyelids and ears or as a rash on the forehead, neck, and lateral face,” Dr. Dunnick said. “However, in general, once the dye has ‘set,’ it is nonallergenic.”

Dr. Dunnick said a worrisome fact is the false labeling of hair dye ingredients. A recent study at New York University analyzed hair dyes using high-performance liquid chromatography (HPLC) and found that five of 51 hair dyes claiming to be “PPD-free” contained PPD. Some patients allergic to PPD can safely use para-toluenediamine sulfate (PTDS) as an alternative, but she recommends patch testing to confirm the culprit ingredient then give accurate and personalized product recommendations.

Drs. Rogge and Dunnick agree that as beauty and skin care trends continue to evolve at a rapid pace, dermatologists are encouraged to increase their vigilance and help patients navigate the growing risks associated with popular cosmetic products and online-driven health claims.