Emerging Allergens and New Sources of Contact Dermatitis

Conclusions

• Isothiazolinones remain a major cause of allergic contact dermatitis in the U.S., but their sources have shifted beyond personal care products to include medical products, gloves, and leather items.
• Regulatory restrictions appear to reduce patch test positivity for some preservatives, showing that policy changes can meaningfully alter allergen exposure patterns.
• Benzoates, especially benzyl alcohol and related compounds, are emerging preservative allergens that can cause both delayed dermatitis and immediate hypersensitivity reactions.
• Because benzoates are ubiquitous and their cross-reactivity is unclear, avoidance counseling often needs to treat them as a class until better data are available.
• Oxidized terpenes such as hydroperoxides of linalool and limonene are important fragrance allergens, particularly in essential oils and other “natural” products.
• Fragrance testing and avoidance are challenging because standard screens may miss relevant cases and irritant reactions are common.
• Nickel allergy remains highly relevant, but newer exposure sources include wearable devices, phone accessories, cosmetic applicators, and microneedling tools.
• Higher-concentration nickel patch testing can improve case detection without substantially increasing irritant reactions.
• Cyanoacrylates are increasingly important allergens in both cosmetic and medical glues and can produce severe localized or disseminated dermatitis.
• When cyanoacrylate allergy is suspected, testing must be tailored to the specific exposure, and tape stripping may be needed when routine patch testing is falsely negative.