Two Cases of Less Common Clinical Presentations of Allergic Contact Dermatitis to Acrylates in <scp>UV</scp> ‐Cured Nail Polish

The first cases of allergic contact dermatitis (ACD) to (meth)acrylates and cyanoacrylates in polymerised resins for artificial nails were described decades ago. However, such cases are now increasingly reported, driven by the wide use of permanent and semi-permanent acrylic nail polishes, either UV-cured or self-curing, applied in beauty salons or at home using manicure kits often purchased online. We herein report two atypical clinical presentations of ACD to acrylates. A 43-year-old woman, with no personal or family history of atopy but a history of earlobe dermatitis related to wearing costume jewellery, experienced periungual vesicles and a burning sensation after the second application of a semi-permanent nail polish, cured at home under a UV lamp (Figure 1D). The lesions rapidly evolved, and after a few weeks, she presented with mild pulpitis affecting all 10 fingers, together with distal subungual haemorrhages and hematomas. Nail detachment was observed, without associated subungual hyperkeratosis or paronychia. The cuticles, proximal nail folds, and the remainder of the skin were normal (Figure 1A–C). On further questioning, she reported a recent episode of mild, transient cheilitis and slight erythema of the upper chest. A 37-year-old woman, with a history of childhood atopic dermatitis but no personal or family history of psoriasis, presented with psoriasiform nail changes evolving over 2 years, clinically characterised by distal onycholysis with nail bed erythema, salmon patches, and discrete hyperkeratosis, without paronychia or pulpitis (Figure 2A,B). No other cutaneous abnormalities were noted. She reported applying a semi-permanent UV-cured nail polish at home, which she had reapplied every 3 weeks for the previous 4 years. In both patients, toenails were unaffected, and atypical ACD was suspected. Patch tests were performed with the European baseline series, along with additional haptens recommended by the REVIDAL-GERDA network (Réseau de Vigilance en Dermato-Allergologie du Groupe d'Étude et de Recherche en Dermato-Allergologie), and an acrylate series. All preparations were mounted on IQ Ultra Chambers (Chemotechnique Diagnostics, Vellinge, Sweden), occluded for 2 days with Opertape (Iberhospitex, Innovative Health Technologies, Barcelona, Spain), and read on days (D) 2 and D3 according to ESCD guidelines [1]. A delayed reading on D7 was performed at home, with patients asked to send photographs of any late positive reactions. For the first patient, patch testing with 2-hydroxyethyl methacrylate 2.0% pet elicited a strong positive reaction (+++ on D2 and D3), as did 2-hydroxyethyl acrylate 0.1% pet and ethyl acrylate 0.1% pet (++ on D2 and D3) (Figure 1E). Reactions to 1,6-hexanediol diacrylate 0.1% pet and ethylene glycol dimethacrylate 2.0% pet were weakly positive (+ on D3). For the second patient, 2-hydroxyethyl methacrylate 2.0% pet and 2-hydroxyethyl acrylate 0.1% pet elicited strong positive reactions (+++ on D2 and D3), while ethylene glycol dimethacrylate 2.0% pet induced a weaker response (+ on D2 and D3) (Figure 2C,D). In both patients, lesions resolved within a few months after discontinuation of semi-permanent nail polish use. In ACD to (meth)acrylates from artificial nails, ACD predominantly affects the hands in approximately 80% of cases [2]. Nail lesions are frequent, usually associated with periungual skin involvement, and may occasionally be accompanied by eczema at distant sites, possibly through self-transfer [3]. In some instances, ACD may only present as isolated digital pain, without visible skin lesions [3]. Atypical clinical forms may lead to diagnostic uncertainties or even diagnostic and therapeutic errors, which occurred in our second patient over a 2-year period. ACD presenting as pseudo-psoriatic nail changes has been rarely described in the literature in this setting, mainly presenting as onycholysis and subungual hyperkeratosis [4-6]. The presence of more typical nail psoriasis signs, such as salmon patches, has only been rarely reported [7]. Similarly, subungual haemorrhages that might initially be suggestive of autoimmune acral disorders are rarely described in this context [8]. These two cases highlight that any nail changes in users of artificial nails or nail polish should raise suspicion of ACD, even in the absence of pulpitis and paronychia. Differential diagnoses include nail psoriasis, lichen planus, onychomycosis, and trauma. ACD should be considered when nail involvement occurs without psoriatic or lichenoid skin or mucosal lesions, without arthralgia, or when mycological cultures are negative. Persistence of nail lesions despite appropriate treatment should lead clinicians to consider acrylate allergy and perform patch testing. The use of at-home kits and non-professional UV-curing nail polishes is associated with a higher risk of acrylate sensitisation [3]. Accordingly, European Union (EU) regulation introduced in 2021 restricted the use of 2-hydroxyethyl methacrylate (HEMA) and di-HEMA in nail cosmetics to professional use only [9]. However, Wilkinson et al. reported that this legislation did not significantly reduce the incidence of acrylate-induced ACD from nail products [10]: HEMA is not completely banned and continues to be used by professionals; additionally, many (meth)acrylates exhibit immunological cross-reactivity, and most nail products contain several different (meth)acrylates, which results in the label “HEMA-free” not being a guarantee of safety; finally, online sales of nail products make compliance with EU regulation and product control more difficult. Similarly, recent Italian data confirmed a rising trend in ACD to 2-HEMA despite existing EU regulations [11]. L.V.: conceptualization, visualisation, writing – original draft preparation, writing – review and editing. Q.S.: investigation, writing – review and editing. O.D.: project administration, resources, supervision, writing – review and editing. A.M.: investigation, writing – review and editing. N.R.P.: conceptualization, investigation, methodology, project administration, supervision, visualisation, writing – original draft preparation, writing – review and editing. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.