Addressing diagnostic challenges in suspected contact dermatitis to cosmetics: Can standard series and patient material suffice for patch test?

Dear Editor,

Contact dermatitis to cosmetics has shown a variable prevalence ranging from 9.8 to 16.5%, among all suspected cases of contact dermatitis.^1,2 The commonly implicated allergens in patients with cosmetic contact dermatitis include cetrimonium bromide (CTAB), p-phenylenediamine (PPD) and fragrance mix.³ There are several allergens like p-phenylenediamine, fragrance mix, colophony, etc., in the cosmetic series which are also a part of the Indian Standard Series (ISS).

In this study, we evaluated the patch test positivity to allergens in the cosmetic series in patients with suspected allergic contact dermatitis to cosmetics and determined the common allergens which were a part of ISS. The patch test records of adult patients (≥18 years) with suspected contact dermatitis to cosmetics attending our department between January and December 2022 were analysed. All patients were patch tested with the Indian cosmetic series and relevant patient material.

Of the 60 eligible patients, 24 (40%) were males and 36 (60%) females between 18 and 75 years (mean age 40.4 ± 12.4 years) of age. Thirty seven patients (61.7%) had diffuse hyperpigmentation, i.e., non-eczematous pigmented contact dermatitis (PCD), while the remaining 23 (38.3%) had acute to subacute dermatitis. All patients had a history of cosmetic use including hair dye (n = 49), hair oils (n = 42), shampoos and cleansers (n = 38), skin-lightening creams (n = 35), perfumes/deodorants (n = 32), moisturising creams (n = 32), bindi/sindoor (n = 14), shaving creams (n = 12), lipsticks (n = 8) and sunscreens (n = 6).

Patch test reading was taken at 48 (day 2) and 96 h (day 4) after patch test application. The day 4 reading was regarded as confirmatory. Twenty one patients (35%) demonstrated a positive patch test reaction to allergens of the cosmetic series and/or patient material. Interestingly, a higher percentage of patients with acute to subacute allergic cosmetic dermatitis (12/23; 52.2%) had positive patch test reactions compared to those with PCD (9/37; 24.3%) (p = 0.02). The primary allergens identified in the cosmetic series were PPD, colophony and thiomersal. Moreover, there was a significant overlap between allergens commonly found in the ISS and cosmetic series, including PPD (n = 9), colophony (n = 3), fragrance mix (n = 2) and paraben (n = 2). Among the 16 patients who reacted positively to the cosmetic series, in 13 patients, the allergens were also a part of the ISS, yielding a statistically insignificant difference in positivity rates (p = 0.52) [Table 1].

In our study, out of 60 suspected cases of contact dermatitis, 21 (35%) patients had a positive patch test to allergens of the cosmetic series and/or patient material. In some previous studies from India, the positivity with the cosmetic series has varied from 59.2 to 72.6%.^3,4 This low positivity rate in our study is possible because of the large number of patients with PCD, where the patch test positivity is low. Ghuse et al. reported 30% (15/50 patients) patch test positivity in patients of facial melanosis suspected to be caused by contact allergens. An additional five (10%) patients were photopatch test positive.⁵ Similarly, Hassan et al. showed that among eight patients of Riehl’s melanosis, only two (25%) had a positive patch test for allergens of the cosmetic series.⁶ The most common allergen detected by Sharma et al. on positive patch testing, in 72.8% (52/74) patients with PCD were cetrimonium bromide (CTAB) and gallate mix.³ However, gallate mix has been removed from the current cosmetic series and this may be contributing to the low yield of positive results, especially in patients with PCD.

Rastogi et al. evaluated 50 patients of suspected cosmetics-induced facial dermatoses and reported that positive reactions occurred significantly more commonly with ISS than with allergens of the cosmetic series (p = 0.053). In their study, PPD was the most common allergen seen in nine (18%) patients which are there in both ISS and the cosmetic series. NiSO₄ was positive in eight patients (16%); which is not a part of the cosmetic series.⁷ Many allergens in the cosmetic series that are commonly implicated as the cause of cosmetic dermatitis are present in ISS too.

Patch testing with the standard series may miss some possible allergens and it would be prudent to patch test with the cosmetic series in all patients suspected to have cosmetic dermatitis. However, the standard series and the patient’s own material may be patch-tested to detect the causative allergens in resource-limited settings. Moreover, there is a considerable difference in the cost of ISS (costs approx. 100 INR) and the cosmetic series (costs approx. 200 INR) (Systopic Laboratories, New Delhi).

Hence, patch testing with ISS and patient material appears to be a reasonable and cost-effective alternative in patients with suspected contact dermatitis to cosmetics, in case of non-availability of cosmetic series and cost constraints.