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Allergies: an underrated factor in alopecia pathogenesis

Presented by
Prof. Natasha Mesinkovska, UC Irvine School of Medicine, CA, USA
Conference
AAD VMX 2021
Several interesting novel treatment options will soon be available for different forms of hair loss. Also, scalp allergic contact dermatitis may be an underestimated cause of hair loss.

In the past years, novel treatment choices for alopecia areata (AA) have emerged, including the Janus Kinase (JAK) inhibitors. “Unfortunately, trials slowed down due to the pandemic, and all 3 approved JAK inhibitors –ruxolitinib, tofacitinib, and baricitinib­– have no indication for AA,” said Prof. Natasha Mesinkovska (UC Irvine School of Medicine, CA, USA). Based on currently available data, one can expect response rates of 46–75%. The agents are well tolerated but expensive. “Long-term use is needed; when the medication is discontinued, hair falls out again,” said Prof. Mesinkovska. In addition, AA is a chronic condition, and sometimes after an initial response, hair still falls out despite continued JAK inhibitor treatment. Although the agents have been associated with a risk of herpes zoster, the risk is small.

JAK inhibitors have also demonstrated to be effective in children and adolescents with hair loss and in alopecia universalis. Even in patients who did not have any hair for years, regrowth has been observed. Unfortunately, about one-third of patients do not respond to treatment. Whether higher doses or longer treatment periods might be justified in these patients remains unclear. Other options currently under investigation are dupilumab, apremilast, and ustekinumab. The selective sphingosine-1-phosphate (S1P) receptor modulator etrasimod may be an interesting novel different pathway in AA.

Allergies contribute to AA

Allergies seem to play a role in AA. In a histopathology study, an eosinophilic infiltrate around the hair bulbs of AA patients was detected in 30.8% of cases in the acute stage but only in 7.7% in the chronic stage [2]. A higher risk of allergic disease such as rhinitis, asthma, and atopic dermatitis (AD) has been reported in AA. One study found that AA patients had higher IgE concentrations, and dust mite allergy against was associated with early-onset AA and severe AA [3]. Mast cells were also found in histologic samples of AA patients. Patients with AA have a 2.6 time increased risk for AD. “We all notice a seasonal pattern in AA with more flares in spring and late autumn,” Prof. Mesinkovska said. These flares coincide with flare frequencies of patients with AD. “This is the rationale to try antihistamines in AA,” Prof. Mesinkovska suggested. Antihistamines such as fexofenadine might be able to enhance hair regrowth. According to Prof. Mesinkovska, their use should be considered in the high-risk seasons: autumn and spring.

A potential novel treatment option for AA patients may be the IL-4/13 antagonist dupilumab. However, the role of this biologic is controversial: some patients with new-onset alopecia had hair regrowth after they were treated with dupilumab for their AD but other patients developed AA after having been treated with dupilumab for their AD.

Scalp allergic contact dermatitis: another cause of alopecia

Many hair products can potentially cause scalp allergic contact dermatitis (ACD). Typical symptoms are erythema (25%), pruritus or itching (22%), and scale (10%). Of note, only 9.3% of patients suffer from scalp dermatitis solely. In most cases, signs can be found elsewhere on the body, including neck, face, and forehead. A review demonstrated that hair dye (most frequently phenylenediamine) is responsible for most ACD cases (48%), another 27% are caused by shampoo, and 8% by topical minoxidil. Alopecia develops in about 10% of ACD cases. To detect the culprit, a full history of allergies, a body exam, and a diagnostic biopsy are warranted. In addition, a patch test should be performed.

Frontal fibrosing alopecia (FFA) is a chronic cicatricial alopecia with unknown aetiology and a rising incidence worldwide. In previous years, a controversy arose about a possible correlation between facial sunscreen use and development of frontal fibrosing alopecia. A study found a high use of sunscreens in women with FFA [4]. A Brazilian case-control study in a multiracial population found a positive association between FFA and the use of moisturisers, facial soap, and hair straightening with formalin, and a negative association with the use of anti-residue/clarifying shampoo. The authors concluded that their study reinforces the possibility of an exogenous particle triggering FFA [5].

  1. Mesinkovska N. HOT Topics: Alopecia. Session S027, AAD VMX 2021, 23-25 April.
  2. Yoon TY, et al. JAMA Dermatology 2014;150(9):952-6.
  3. Li SF, et al. Clin Exp Dermatol 2015;40(2):171-6.
  4. Aldoori N, et al. Br J Dermatol 2016;175(4):762-7.
  5. Ramos PM, et al. J Am Acad Dermatol 2021;84(3):712-8.

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