Contact Dermatitis and Hair Care 

It is well established that hair care products cause irritant and/or allergic contact dermatitis. Hair care products can also leave a residue that remains on the skin of the face, scalp, and back for hours, even after rinsing shampoo and conditioner.¹ Product residue can be deposited while rinsing, transferred from the hair to the skin, or transferred from a towel or pillowcase to the skin. Hair care products can have a significant effect on the health of the skin, and contribute to other skin issues, including acne, dry scalp, and even hair shedding. 

Contact dermatitis from hair care products can be due to either irritants or allergens, and there can be an overlap.^2,3 Irritant contact dermatitis (ICD) is more common, and characterized by dermatitis that develops with first exposure to the product. Conversely, allergic contact dermatitis (ACD) requires prior exposure to an allergen, and is a delayed, cell-mediated hypersensitivity reaction. 

Personal-care product-related contact dermatitis is on the rise. Positive patch tests to personal care products more than doubled between 1996 and 2016.³ North American Contact Dermatitis Group (NACDG) patch test data also showed that 9% of 38,775 patients experienced a reaction to hair care between 2001 and 2016.⁴ The most common ingredients in hair care associated with contact dermatitis are preservatives, fragrance, surfactants, dyes, emulsifiers and adhesives.^4,5 

Of all personal care products, hair care is the third most common source of allergen exposure. Hair care products such as shampoos and conditioners are major contributors to contact dermatitis.⁵ Many dermatologist-recommended over-the-counter and prescription dandruff shampoos contain formaldehyde-releasing ingredients and other allergens^.6

Contact dermatitis from hair care products may present in “rinse off” areas, on the eyelids, neck, and sides of the face. It can also appear on the scalp, hands, or trunk, or have a generalized distribution. It is not uncommon for contact dermatitis from hair care to spare the scalp. Erythema, flaking, and pruritus are the most common symptoms of contact dermatitis, and burning, discomfort, and hair shedding can occur as well. Pain and/ or edema can also occur. Dermatitis is most likely to develop in areas that come in contact with rinse-off hair care products, such as the hairline, nape of the neck, ears, and eyelids.⁵

Contact dermatitis caused by hair care ingredients can appear on the scalp but is uncommon on the scalp alone because the scalp may be relatively protected from contact dermatitis.^2,5 The scalp has thicker skin and greater sebum production,² and there is also a greater amount of regulatory T cells around the follicles^;5 these factors may offer the scalp protection from contact dermatitis. 

THE IMPORTANCE OF PRODUCT TESTING (RIPT) 

Human repeat insult patch testing (RIPT) involves applying a specific ingredient or final product formula to the skin multiple times in order to evaluate the likelihood that they will cause irritation or allergic contact dermatitis. To establish a “safe for sensitive skin” claim, traditional RIPT testing can be modified to include a panel of subjects with self-perceived sensitive skin. Personal-care and cosmetic companies are not mandated to perform RIPT testing on any products– including hair care. 

“Frontal fibrosing alopecia (FFA) is a scarring alopecia that is a variant of lichen planopilaris (LPP). Its incidence is growing, with the exact cause unknown. A higher frequency of contact allergy has been observed in FFA, though a causal relationship has not been established. An association with sunscreen use and FFA has also been identified, but the studies have limitations and are not definitive. Some of the most common allergens in FFA include gallates, hydroperoxides of linalool, fragrance, propolis, metals (including nickel sulfate, cobalt chloride), balsam of Peru (Myroxylon pereirae[MP]), methylisothiazolinone, iodopropynyl butylcarbamate, methyldibromo glutaronitrile (MDBGN), and benzophenone-4.⁸

In a study of 42 patients with LPP/FFA referred for patch testing, 76.2% had positive reactions to clinically relevant allergens in personal care products applied to the face and scalp.⁹ Allergen avoidance may be able to help reduce inflammation locally and lead to symptom improvement.^8,9

In a 6-month randomized controlled trial of 53 patients (including controls) with female pattern hair loss and LPP who used a fragrance-free, non-comedogenic hair care regimen that avoids many common allergens, there was significantly less hair shedding in the experimental group compared to control. In addition, patients with LPP had a significant reduction in their Lichen Planopilaris Activity Index (LPPAI) score at 6 months compared to baseline, indicating decreased LPP activity.¹⁰ 

OCCUPATION-RELATED DERMATITIS 

It is believed that between 70% and 90% of work-related skin conditions are triggered by contact with an allergen or irritant,¹¹ and up to 50% of hairdressers develop hand contact dermatitis within 3 years of beginning work.¹² In contrast to clients who experience skin reactions on their head, neck, and face after coloring their hair, hairstylists often develop contact dermatitis on their hands (this can be a hazard for healthcare and other workers who wash their hands frequently as well). 

Gloves are recommended to protect hairdressers’ skin when applying treatments such as hair dye and straightening solutions. However, rubber latex, vinyl, and other common materials may not be able to eliminate the risk of allergens causing contact dermatitis. In addition, ingredients in the gloves themselves may be another source of allergens that affect the skin.⁵ 

COMMON INGREDIENTS LINKED WITH CONTACT DERMATITIS

PRESERVATIVES

Preservatives are used to prevent microbial growth in personal-care products. According to a retrospective analysis performed by the NACDG, after Paraphenylenediamine (PPD), the second and third most common allergens in hair care products are the preservatives methylisothiazolinone (MI) and methylchloroisothiazolinone (MCI). MI is also the most frequently used preservative in shampoos, as MCI/MI has been identified in up to 51% of shampoo formulations.⁵

Many preservatives used in hair care are known to release formaldehyde. Quaternium-15 releases more formaldehyde than some others, and in one study was identified as the likely cause of scalp contact dermatitis in 5% of patients. The formaldehyde-releasing preservatives DMDM hydantoin, imidazolidinyl urea, diazolidinyl urea, and 2-bromo-2-nitropropane-1,3 diol are weaker sensitizers than formaldehyde itself and may be an inducer of contact dermatitis separate from formaldehyde allergy.⁵

It’s also worth noting that the parabens, while widely used as preservatives in hair care and other cosmetic products, pose a very low risk of contact dermatitis.⁵

FRAGRANCE

Fragrances can be any additive to a product that has a pleasing smell, or in the case of masking fragrances, the scent may be neutral/unscented. Fragrance allergy is found in 1% to 4% of the general population, while 8% to 15% of those with allergic contact dermatitis react to fragrances.⁷ Fragrance is commonly used in hair care products, and is even found in medicated shampoos, such as ketoconazole.5 Fragrance mix 1 and fragrance mix 2 are the most commonly used mixes tested during contact dermatitis evaluation. 

It is important to note that even “natural” fragrances can cause contact dermatitis. The hydroperoxides of linalool and limonene are strong sensitizers, and are considered some of the most common allergens, based on NACDG patch test data.⁵ Both are tested in fragrance mix 2. Products labeled as “unscented” may not be truly fragrance free and often contain masking fragrance. 

SURFACTANTS 

Shampoo and conditioner are the hair care products that most commonly cause irritant contact dermatitis.⁴ Potentially harsh surfactants are commonplace in shampoo formulations, and sulfates are among the most common. Although sodium lauryl sulfate is a strong irritant, this ingredient does not directly cause allergic contact dermatitis. Another member of this ingredient family, sodium laureth sulfate, may be less irritating.⁵ Alkyl glucosides are related to sodium lauryl sulfate, but are “natural.” Glucosides are manufactured by condensing glucose with a plant-based fatty alcohol. The most common glucosides are decyl followed by lauryl glucoside. The rate of contact allergy is low, with 2% of tested individuals being positive on the NACDG series, tested over a 10-year period.⁴

Compared to sulfates, cocamidopropyl betaine (CAPB) is a milder surfactant that gained popularity as a “no tears” cleansing ingredient. The rate of contact dermatitis caused by CAPB has increased, and this ingredient has been found to be the third most common allergen in shampoos and conditioners.⁵ However, CAPB itself is not a strong allergen. The impurities that remain during CAPB manufacturing—specifically amidoamine (AA) and 3-dimethylaminopropylamine—may be the cause of many cases of contact dermatitis.⁵

HAIR DYES AND OTHER SOURCES OF IRRITANTS/ ALLERGENS 

Hair dyes are a common cause of contact dermatitis, and the most common product associated with scalp ACD. p-Phenylenediamine (PPD) is the most common cause of ACD to hair dye.²

OTHER INGREDIENTS 

Various other ingredients have been linked to irritant and allergic contact dermatitis of the scalp. Some of these include propylene glycol, found in products including minoxidil solution; nickel (most commonly from hair accessories); certain adhesives; ammonium persulfate; and glyceryl thioglycolate found in perms.^2,4,5

CONCLUSION 

Hair care products are a significant source of irritants and allergens that can contribute to contact dermatitis. It is important to note that contact dermatitis due to hair care products may present on rinse-off areas, and other areas of the skin, and can spare the scalp. Hair care products that are formulated with ingredients chosen to be less likely allergens/irritants may be useful for individuals with sensitive skin or chronic dermatitis. 

1. Rubin IK, Gourion-Arsiquaud S. Deposition and Retention of Hair Care Product Residue Over Time on Specific Skin Areas. J Drugs Dermatol. 2020;19:419-423. 

2. Pham CT, Juhasz M, Lin J et al. Allergic Contact Dermatitis of the Scalp Associated With Scalp Applied Products: A Systematic Review of Topical Allergens. Dermatitis. 2022; 33:235.248. 

3. Warshaw EM, Schlarbaum JP, Silverberg JI et al. Contact dermatitis to personal care products is increasing (but different!) in males and females: North American Contact Dermatitis Group data, 1996-2016. J Am Acad Dermatol. 2021;85:1446-1455. 

4. Warshaw EM, Ruggiero JL, DeKoven JG, etl. al. Contact Dermatitis Associated With Hair Care Products: A Retrospective Analysis of the North American Contact Dermatitis Group Data, 2001-2016. Dermatitis. 2022;33:91-102. 

5. Karim M, Klein EJ, Nohria A, et. al. Potential for Allergic Contact Dermatitis in Popular Hair Care Practices and Ingredients. Dermatitis. 2023;34:484-491. 

6. Flanagan KE, Pathoulas JT, Walker CJ, et al. Legislative update: Regulating ingredients in personal care products. J Am Acad Dermatol. 2021;84:1780-1781. 

7. Fragrance and Perfume Allergy and Eczema FAQ. National Eczema Association. https://nationaleczema.org/blog/fragrances-perfumes-eczema-allergy. Published May 29, 2013. Updated September 30, 2021. Accessed September 26, 2024. 

8. George SE, Rodriguez I, Adeler BL, et al. Tangled Truths: Unraveling the Link Between Frontal Fibrosing Alopecia and Allergic Contact Dermatitis. Cutis. 2024;113: 119-122. 

9. Prasad S, Marks DH, Burns LJ, et al. Patch testing and contact allergen avoidance in patients with lichen planopilaris and/or front fibrosing alopecia: A cohort study. J Am Acad Dermatol. 2020;83:659-661. 

10. Ali S, Collins M, Pupo Wiss I et al. Use of a scalp purifying shampoo in the treatment of lichen planopilaris and female pattern hair loss. Society for Investigative Dermatology (SID) annual meeting; May 2022; Portland, Oregon; https://www.jidonline. 

11. Rashid RB, Shim TN. Contact Dermatitis. BMJ. 2016;353:i3299 

12. Worth A, Arshad SH, Sheikh A. Occupational dermatitis in a hairdresser. BMJ. 2007;335:399.