Prevalence of Contact Allergens in Natural Skin Care Products From US Commercial Retailers

Abstract

This quality improvement study assesses the prevalence of contact allergens in personal care products classified as clean or natural among 3 national retailers in the US.

Contact dermatitis is the fifth most prevalent skin disease in the US,¹ exceeding $1.5 billion in direct annual medical costs.² Personal care products (PCPs) such as soaps, lotions, and fragrances contain ingredients that may cause allergic contact dermatitis (ACD).² The prevalence of PCP-related dermatitis increased 2.7-fold between 1996 and 2016.³ Increasing numbers of natural PCPs (NPCPs) have been marketed to consumers concerned about the effects of chemicals on the skin, such as irritation and allergic reactions. Retail chains such as supermarkets are the most prolific distributors of NPCPs, accounting for 41.7% of worldwide NPCP revenue in 2019.⁴ The US Food and Drug Administration (FDA) has not defined clean or natural, allowing sellers to freely advertise with these terms that imply safety and health benefits.

Contact dermatitis is only preventable by identification and avoidance of causative substances,⁵ but patients may find avoidance difficult owing to complex ingredient names.² Confusion may be compounded by NPCP manufacturers frequently listing botanical extracts (leading causes of contact dermatitis and photosensitization) by their Latin names.

Little is known about the allergenic potential of NPCPs. The increasing prevalence of ACD, expanding NPCP industry, and lack of regulation by the FDA underscore the need for objective study. Therefore, we evaluated 1651 NPCPs from 3 national retailers in the US for the presence of allergens using the American Contact Dermatitis Society’s (ACDS) Contact Allergen Management Program (CAMP), a web-based resource for patients with ACD.

Methods

The Stanford University School of Medicine institutional review board deemed this quality improvement study exempt and waived informed consent because it was non–human participant research. We followed the SQUIRE reporting guideline.

Using Python, version 3.8.9, we extracted product ingredient lists of NPCPs from 3 national retailer websites from January to March 2022: Target.com, Walgreens.com, and WholeFoodsMarket.com. Using filters on the websites, products categorized as natural or clean were included. Products without allergens were manually checked. Products considered irrelevant (cotton rounds, scrub brushes, and oral multivitamins), duplicates (doubly listed due to multiple container sizes), and products without readily accessible ingredient lists were excluded.

Allergen was defined as a contact sensitizer according to the CAMP database. Ingredients were cross-referenced with the 191 contact allergens in CAMP. Identified allergenic ingredients and the number of allergens per product were recorded. Clinical prevalence for identified allergens was determined by cross-referencing earlier work describing the 100 allergens most frequently eliciting positive reactions using ACDS patch tests (Table 1).⁶

Table 1. Clinical Prevalence of Contact Allergens and Products Containing Them.

Allergena	Clinical prevalence, rankb	NPCPs with ingredient, No. (%) (N = 1651)
Fragrance mixc	1	605 (36.6)
Eugenolc,d	1	40 (2.4)
Hexyl cinnamalc,d	3	57 (3.5)
Cinnamic alcoholc,d	3	1 (0.1)
MCI, MITd	9	23 (1.4)
Propylene glycol	10	162 (9.8)
Iodopropynyl butylcarbamate	11	37 (2.2)
P-phenylenediamine	13	2 (0.1)
Propolis	14	7 (0.4)
Cocamidopropyl betaine	20	129 (7.8)
Linalool	21	297 (18.0)
Benzoyl peroxide	28	2 (0.1)
Dimethylaminopropylamine	30	1 (0.1)
Decyl glucoside	31	98 (5.9)
Limonenec	32	309 (18.7)
Rosin	35	2 (0.1)
Diazolidinyl urea	41	17 (1.0)
Benzoate	44	428 (25.9)
Sodium benzoate	44	381 (23.1)
Benzyl benzoate	44	44 (2.7)
Benzoic acid	44	117 (7.1)
Benzophenone-4	46	8 (0.5)
Tea tree (melaleuca) oil	52	77 (4.7)
Benzalkonium chloride	54	3 (0.2)
Benzyl salicylate	58	63 (3.8)
Lanoline	59	43 (2.6)
DMDM hydantoin	60	14 (0.8)
Cocamide DEA	61	1 (0.1)
Carmine	62	19 (1.2)
Tocopherolf	63	792 (48.0)
Ammonium persulfate	64	1 (0.1)
Benzyl alcoholc	65	189 (11.4)
Phenoxyethanol	70	776 (47.0)
Benzophenone-3	71	5 (0.3)
Lauryl glucoside	82	57 (3.5)
Chlorhexidine digluconate	83	7 (0.4)
Propyl gallate	89	1 (0.1)
Triethanolamine	90	18 (1.1)
Amyl cinnamalc	96	31 (1.9)
Jasminec	97	32 (1.9)
Isoeugenolc	98	2 (0.1)
Sorbic acid	99	37 (2.2)
Peppermintc	100	45 (2.7)
Cetyl alcohold,g	NA	268 (16.2)
Stearyl alcohold,g	NA	100 (6.1)
Lyralc,g,h	NA	10 (0.6)
BHTg	NA	2 (0.1)

Abbreviations: BHT, butylated hydroxytoluene; DEA, diethanolamine; DMDM, 1,3-dimethylol-5, 5-dimethyl; MCI, methylchloroisothiazolinone; MIT, methylisothiazolinone; NA, not applicable; NPCPs, natural personal care products.

^a Seventy-three unique allergens were identified; the table includes 43 that were among the 100 most clinically prevalent sources of allergic contact dermatitis⁶ and 4 (cetyl alcohol, stearyl alcohol, Lyral, and BHA) that are clinically prevalent but were not among the top 100.

^b Based on data from Scheman et al.⁶

^c Commonly used as fragrance.

^d Clinical prevalence ranks shown are for closely related substances that would elicit a positive reaction: cetyl alcohol and stearyl alcohol (not ranked among the 100 most clinically prevalent allergens) test positive to cetylstearyl alcohol; eugenol is found in fragrance mix; hexyl cinnamal and cinnamic alcohol are common components of Balsam of Peru; and MCI cross-reacts with MIT.

^e Lanolin, lanolin alcohol, and wool alcohol.

^f Tocopherol and vitamin E.

^g Clinically prevalent but not among the 100 most clinically prevalent allergens.

^h Lyral and hydroxyisohexyl 3-cyclohexene carboxaldehyde.

Results

Of the 1756 NPCPs advertised, 105 did not meet inclusion criteria for analysis. Of the remaining 1651 NPCPs, 1555 (94.2%) had at least 1 contact allergen, 1478 (89.5%) contained 1 or more contact allergens from among the 100 most clinically prevalent, and 96 (5.8%) had no contact allergens. The mean (SD) number of contact allergens per product was 4.5 (3.2). There were 73 unique allergens identified, appearing 7487 times on ingredient lists of the 1555 products (Table 2).

Table 2. Summary of Analyses.

	Overall	Walgreens.com	WholeFoodsMarket.com	Target.com
NPCPs, No. (%)
Total analyzed	1651 (100)	393 (100)	203 (100)	1055 (100)
With contact allergens	1555 (94.2)	380 (96.7)	179 (88.2)	996 (94.4)
With top-100 contact allergensa	1478 (89.5)	378 (96.2)	172 (84.7)	928 (87.9)
Allergens per NPCP
Median (IQR)	4 (2-6)	6 (4-8)	3 (1-5)	4 (2-6)
Mean (SD)	4.5 (3.2)	6.4 (3.7)	3.5 (3.0)	4.1 (2.7)
Unique allergens, No.	73	66	37	60
Total allergenic ingredients, No.	7487	2497	707	4283

Abbreviation: NPCP, natural personal care product.

^a The 100 most prevalent causes of acute contact dermatitis.⁶

Discussion

Most of the analyzed NPCPs contained contact allergens, including many fragrances, and 89.5% contained 1 or more of the 100 most prevalent allergens in the ACDS CAMP database. These results suggest a need to educate patients and health care professionals to ensure the public is informed about the products they apply to their skin.

A study limitation is that comparing allergen prevalence in NPCPs vs ordinary PCPs was beyond our scope because retailers did not have a distinct category for nonnatural products. Also, owing to marketing and website differences between retailers, product types (eg, shampoo vs lotion, leave on vs wash off) were not uniformly obtainable; thus, these comparisons were not practicable.

The results suggest that advertising claims that PCPs are natural or clean may not portend health or safety with respect to ACD. This knowledge may enable clinicians to guide consumers toward purchasing decisions that could lessen ACD prevalence and preserve health care resources.