Patch Test Highlights Allergens Impacting Alopecia Areata, Other Hair Conditions

A specific type of patch test for hair care products and allergenic reactions among patients with hair loss due to alopecia areata and related conditions is effective, new findings suggest, as the test allows for robust evidence for tailored clinical management.1

The analysis which resulted in these findings—led by Chengcheng Feng, from the department of dermatology at Nanjing University of Chinese Medicine’s Zhangjiagang TCM Hospital—explored the allergic situation of different hair conditions via a specific type of patch product testing, allowing for a strong basis for personalized disease management.

Fend and colleagues highlighted the widespread implementation of patch testing in the diagnosis of diseases such as contact dermatitis in the dermatology space.2

“The patch test for hair care products includes components such as allergens commonly found in daily scalp care products, metals from scalp-contacting items, commercially available or hospital-compounded topical scalp medications, and pharmaceutical combinations designed to address common sensitizing agents,” Feng et al. wrote. “Therefore, the patch test for hair care products is of significant importance for clinical safety, rational, and precise medication use, as detailed in the following report.”1

Hair Loss and Associated Allergens in Hair Products

Between October - December 2023, the study's investigators assessed 196 patients with diagnoses of hair loss provided through a dermatology department. The population of the study consisted of 110 males and 86 females, and the team highlighted there was an average age of 32.34 ± 7.48 years and a range of 7 - 56 years.

The investigative team noted that 135 patients of these individuals were shown to have androgenetic alopecia, 37 were shown to have alopecia areata, 15 were shown to have telogen effluvium, and 9 with other types of hair loss. The team looked at the results of a review of medical records and hair microscopy images, finding that 109 of the subjects 146 had folliculitis, had head-seborrheic dermatitis, and none demonstrated any signs of having had contact or irritant dermatitis.

The research team used their test to evaluate any potential allergic reactions, with 20 substances being tested. These included 7 haptens which were in scalp care products, 2 metal haptens, and 11 commonly used topical medications and their different combinations. The team's patch test followed a standardized screening protocol using hapten diagnostic kits.

The analysis involved an application of each medication in its original liquid form, with adherence to the manufacturer guidelines. The investigators placed test substances onto normal skin on both sides of the spine and then secured to ensure effective contact with the skin.

Following a period of 48 hours, the would remove the patch chambers and carry out a 30-minute waiting period, seeking to ensure that any pressure-induced erythema would subside prior to any assessment of resulting irritation responses. The investigative team also re-evaluated sensitization reactions at the 72-hour mark. The assessment criteria used to evaluate the findings were based upon guidelines that had been established by the International Contact Dermatitis Research Group.

The team's data analysis involved using SPSS 22.0 statistical software. They would apply the chi-square test with the aim of determining statistical significance, setting a P-value of less than 0.05 as significant.

Overall, there were an array of common allergens identified within hair care products. The investigators found that dodecyl polyglucoside's positivity rate was 10.2% and that the rate of Balsam of Peru had been 8.67%. The research team further reported minoxidil's association with a notable sensitization risk, adding that 5% minoxidil liniment had a positivity rate of 22.96%, and 5% minoxidil tincture had an even higher rate of 27.04%.

However, the team further noted that minoxidil liniment concentration reduction to 2% led to significantly lower rates of positivity, with 4.08% specifically. Among metal-related allergens, it was determined that cobalt chloride showed the highest rate of positivity at 56.63%, followed then by nickel sulfate at 32.65%.

The investigators further highlighted that the combination of Hasonide solution with 5% minoxidil tincture led to a sensitization rate of 16.33%. However, they commented that neither Hasonide solution alone nor its combination with 5% minoxidil liniment had been shown to lead to positive reactions among participants.

Such conclusions indicate that Hasonide solution may lead to sensitization reductions, potentially, for minoxidil tincture as well as liniment formulations.

“In conclusion, with the accelerating pace of modern life, the number of patients with hair disorders is increasing annually,” they wrote. “However, addressing individual variability remains a pressing issue in achieving personalized treatment. This study utilized patch testing with hair care products to investigate allergenic reactions among patients with hair disorders, providing robust evidence for personalized clinical treatments.”1

References

1. Feng, C., Wang, Y., Yang, D. and Shen, H. (2025), Analysis of Common Treatment Drugs and Allergen Sensitization in Hair Loss Patients. J Cosmet Dermatol, 24: e16798. https://doi.org/10.1111/jocd.16798.

2. F. Hao, L. F. Li, H. Gu, and Y. Zou, “Expert Consensus on the Clinical Application of Patch Testing (2020 Revised Edition),” Chinese Journal of Dermatology 4 (2020): 239–243.