PracticalDermatology

Hair care and skincare have long been distinct categories, but hair care products can actually deposit a residue on the scalp, face, and back that can stay on the skin for hours.¹ As a result, hair care products can have a tremendous impact on the skin and can contribute to acne, irritation, allergic contact dermatitis, dry scalp, and even hair loss. Shampoo and conditioner can deposit residue as they rinse down the scalp, face, and body in the shower. Many hair care products are also designed to leave a residue on the hair, and that residue can transfer to the skin directly from the hair or from a towel or pillowcase. For example, an article in Dermatology News referred to hair smoothing products as an acne-causing epidemic,² stating that the skin may be in contact with styling products on a pillowcase all night.

Most hair care products have not traditionally been formulated with the skin in mind. They can be formulated with comedogenic, irritating, and/or allergenic ingredients. Unfortunately, there is also insufficient regulation regarding allergens or harmful chemicals in hair care products.³

Hair care product residue can deposit on the skin

Given that hair care products can get on the skin and stay on the skin for hours, it is important for dermatologists to understand the skin issues that can be associated with hair care products. It is almost impossible to use a hair care product without it getting on the skin.

We recently published a case report that showed hair care products, including rinse-off products like shampoo and conditioner, can leave a residue that remains on the scalp, forehead, cheeks, and upper back for hours. Leave-in styling products can also deposit residue on the skin, with the amount of residue actually increasing over time.¹

Since hair care products can get on the skin and stay on the skin for hours, we believe this makes them skincare products as well.

Hair care and acne

Acne cosmetica is a well-recognized condition, commonly associated with comedogenic skincare products. It was described by Kligman and Mills as being characterized primarily by small closed comedones and occasional papulopustules, localized to the face.⁴ Hair care products can also contribute to acne, though they are an often-overlooked contributor unless a patient presents with classic pomade acne on the forehead. The American Academy of Dermatology (AAD) recognizes that acne cosmetica can be caused by hair care products and describes the condition as tiny bumps on the hairline, forehead, and back of the neck.⁵ We believe hair care products can contribute to acne beyond these areas, and include other parts of the face, as well as the trunk, and may present beyond the classic comedones associated with acne cosmetica.

We published a dermatologist-graded study of 27 patients with mild to moderate acne who used a non-medicated, non-comedogenic, and non-irritating hair care regimen (SEEN Shampoo and SEEN Conditioner) for 8 weeks. At week 8, 70% of subjects with body acne improved, and 52% with face acne improved by dermatologist grading. Results were statistically significant. The shampoo and conditioner were to be used at least three times a week. Subjects were only permitted to use the hair care products provided for the duration of the study.⁶ A representative case from the study is shown. (Figure 1.)

Figure 1. Face at baseline (left) and at 8 weeks after (right) using the non-medicated, non-comedogenic hair care regimen.

Dry, flaky scalp

Dry scalp is a distinct clinical entity from seborrheic dermatitis, characterized by dryness, flaking, and pruritus localized to the scalp, in the absence of visible erythema. It is important to differentiate dry scalp from seborrheic dermatitis, as a gentle, non-medicated shampoo may be indicated, rather than medicated shampoos typically used for seborrheic dermatitis.⁷

In many cases, the etiology of dry scalp may be xerosis, with the dry skin localized to the scalp. Harsh surfactants in hair care may play a role in causing scalp xerosis. Undiagnosed allergic or irritant contact dermatitis may also be the cause of a dry, flaky scalp in a subset of patients.⁸

In a dermatologist graded study, 30 patients with mild to moderate dry, flaky scalp used a non-medicated, non-comedogenic, and non-irritating hair care regimen (SEEN Shampoo and SEEN Conditioner) for 4 weeks. Subjects were to use the shampoo and conditioner a minimum of three times a week. Subjects were not permitted to use any other hair care products, including OTC or prescription products for dandruff.

The overall dry scalp condition was assessed by dermatologist grading using the Investigator Global Assessment (IGA) scale (Table 1). At week 2, 70% of subjects showed improvement in the investigator global assessment (IGA) of the scalp. At week 4, 93% of subjects showed improvement in the IGA of the scalp. These results were statistically significant (Table 2). The mean change from baseline at 4 weeks was -1.53. This represents a mean 67% improvement in the IGA score for the scalp.

At week 2, 70% of subjects reported improvement in pruritus of the scalp. At week 4, 73% of subjects reported improvement in pruritus of the scalp. These results were statistically significant (Table 2). The mean change from baseline at 4 weeks was -1.10. This represents a mean 66% improvement in the scalp pruritus score.

Subjects also completed a self-assessment questionnaire at 2 weeks and 4 weeks. At 4 weeks, 77% agreed “my scalp flaking is improved,” and 73% agreed “my scalp is less dry” (Table 3).

There are several mechanisms by which this hair care regimen likely benefited dry, flaky scalp. The first is the hair products are sulfate-free, and use a mild surfactant that is less drying to the skin. The milder surfactant may have had a benefit on epidermal barrier function, as shampooing with harsh surfactants can repeatedly damage the stratum corneum permeability barrier. Harsh surfactants have been reported to negatively impact overall barrier quality, and promote flaking.⁹ It is also likely that some of the participants had undiagnosed irritant or allergic contact dermatitis.

The hair care products in this study avoid many common allergens. They are also formulated with bisabolol, a naturally-derived ingredient with anti-inflammatory properties.

Allergic contact dermatitis

The hair products commonly associated with allergic contact dermatitis (ACD) of the scalp are hair dyes (41%), shampoos (28%), and conditioners (22%). The most common contact patch test allergens include p-phenylenediamine, nickel, fragrance, balsam of peru, cocamidopropyl betaine/3-dimethylaminopropylamine, and methylchloroisothiazolinone/methylisothiazolinone.¹⁰ Based on data from the North American Contact Dermatitis Group from 2001-2016, 9% had positive patch test results associated with hair care products.¹¹ The incidence of contact dermatitis is also increasing from personal care products, with positive patch tests from personal care products having more than doubled between 1996 and 2016.¹² Surprisingly, even many dermatologist-recommended dandruff shampoos contain common allergens, including formaldehyde releasers.3

Isolated scalp dermatitis due to ACD is actually uncommon, likely because the scalp is relatively protected from contact dermatitis due to its thickness, as well as higher sebum production. A majority of ACD cases from products applied to the scalp appear on areas that come in contact with products when rinsing, such as the face, neck, and ears.¹⁰

It is also worth noting that irritant contact dermatitis (ICD) is even more common than ACD, and many cases of contact dermatitis may involve a combination of ICD and ACD.¹⁰

Hair loss and hair health

Hair follicles are the manufacturing plant for the hair, and many traditional hair products can clog the pores, and/or contain irritants and allergens, potentially impacting the follicle’s health. Data is lacking on how hair products that clog the pores, or having irritants and allergens, contribute to hair health and hair growth. While certain allergens in hair care products have been associated with lichen planopilaris/frontal fibrosing alopecia,¹³ the potential impact of traditional hair care products on non-scarring alopecia are less known.

A recent randomized, controlled clinical trial at Harvard’s Hair Loss Clinic at Massachusetts General Hospital assessed the effects of using a non-medicated, non-comedogenic, non-irritating, and fragrance-free hair care regimen (SEEN Fragrance-Free Shampoo and SEEN Fragrance-Free Conditioner) in 29 patients with female pattern hair loss.¹⁴ The 6-month study included 14 intervention subjects and 15 control subjects, and found that the non-comedogenic, non-irritating, fragrance-free hair care regimen reduced hair shedding by 44% compared to control. The study showed 221 fewer hairs shed per week compared to control. That’s equivalent to 11,492 fewer hairs lost a year, which is more than 10% of the average human head. This study suggests that traditional hair care products may negatively impact hair health and hair growth, by either clogging the pores on the scalp, and/or through irritants and allergens that also affect the follicle. Further research is needed to fully assess the impact of hair care products on hair shedding and hair loss.

In conclusion

As dermatologists, we often discuss skincare regimens with patients. Given that hair care products can leave a residue on the skin for hours, including the scalp, face and back, we propose that as dermatologists we should discuss a patient’s hair care regimen, as well, for relevant conditions. Someone with acne, for example, could be doing all the right things with their medicated regimen and skincare, and then negate some of the benefits by bathing in pore-clogging ingredients every day via their hair care without realizing it.

Our patients deserve hair care products that respect the skin, and don’t contribute to skin issues like acne, eczema, dry scalp or hair loss. I believe that hair care is skincare, and that hair care products should be developed with the same rigorous testing as skincare products, including comedogenicity and repeat insult patch testing (RIPT) testing.

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. Dermatology News. Smooth hair- an acne-causing epidemic. Available at: https://www.mdedge.com/dermatology/article/108161/acne/smooth-hair-acne-causing-epidemic.

3. Flanagan KE, Pathoulas JT, Walker CJ et al. Legislative update: Regulating ingredients in personal care products. J Am Acad Dermatol 2021;84:1780-1.

4. Kligman AH, Mills OH. Acne cosmetica. Arch Dermatol 1972;106:843-50.

5. American Academy of Dermatology. Are your hair care products causing breakouts? Available at: https://www.aad.org/hair careproducts. Accessed 5/2/2022.

6. Rubin IK. Efficacy of a Non-Comedogenic Hair Care Regimen for the Reduction of Mild-to-Moderate Truncal and Facial Acne: A Single-Arm 8-Week Study. J Drugs Dermatol 202;20:690-693.

7. American Academy of Dermatology. Is your dry scalp something more serious? https://www.aad.org/public/everyday-care/hair-scalp-care/scalp/dry-scalp-conditions. Accessed 5/2/2022.

8. American Academy of Dermatology. 10 reasons your scalp itches and how to get relief. https://www.aad.org/public/everyday-care/itchy-skin/itch-relief/relieve-scalp-itch. Accessed 5/2/2022.

9. Turner GA, Hoptroff M, Harding CR. Stratum corneum dysfunction in dandruff. Int J Cosmet Sci 2012;34:298-306.

10. 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.

11. Warshaw EM, Ruggiero, JL, DeKoven JG et al. Contact dermatitis associated with hair care products: A retrospective analysis of the North American Contact Dermatitis Group, 2001-2016. Dermatitis 2022;33:91-102.

12. 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.

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

14. 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.org/article/S0022-202X(22)01398-7/fulltext