Allergic contact dermatitis in response to contact with polychloroprene

Abstract

Polychloroprene (trade name neoprene) is a rubber material, which is in common use as it is waterproof, stretchable, and resistant to physical and chemicals damage.¹ Polychloroprene is applied in various diving equipment, goggles, gloves, shoe insoles, protective clothing, and orthopaedic braces and new areas of usage are developing continuously. Polychloroprene often contains residues of thiourea compounds, which have a sensitising potential and thus may cause allergic contact dermatitis (ACD).

Between 2009 and 2022, seven patients suspected to have developed dermatitis in response to contact with polychloroprene, were examined at the Department of Occupational Medicine, Haukeland University Hospital, Bergen, Norway. The patients were all men and with a mean age of 38 years (minimum of 19 years, maximum of 47 years) at debut of dermatitis (Table 1).

Three patients had no relevant occupational exposures. Two of the patients had used diving equipment during leisure (kayak paddling dry suit, wet suits, diving socks and goggles) (patients 1 and 2), while one patient had used shoe insoles and a weight west (patient 3).

Four patients had relevant exposures at work as well as during leisure. Three patients (patient 4, 5, and 6) worked at offshore installations and used survival suits with polychloroprene cuffs during helicopter transportation. All offshore workers had relevant leisure exposures; two had used orthopaedic knee braces during sport activities (patient 4 and 5) while one had used rubber boots (patient 6). One patient (patient 7) had used a survival suit at work in the Navy and a wet suit during leisure.

Information derived from the patients' medical records stated that two patients had a childhood history of atopic dermatitis (patient 3 and 7). Patient 7 was diagnosed with dyshidrotic dermatitis at a later stage. Patient 5 had symptoms of dyshidrotic dermatitis and/or nummular dermatitis, while patient 6 had previous episodes of psoriasis.

Patch testing was performed on the upper back of each patient using Chemotechnique patch test series, IQ ultra chambers (Chemotechnique Diagnostics, Vellinge, Sweden) and Primafix tape (Smith & Nephew, London, UK). Patch tests were removed after 48 h and readings were performed one or more of the following days: day three (D3), day four (D4) and day seven (D7).² All patients were tested with the European baseline series (S-1000). All patients except patient 3 were tested with the Rubber additives series (R-1000). Patient 3 was tested with the Shoe series (SH-1000) as he presented foot dermatitis. The Rubber additives series included the following thiourea compounds: thiourea (0.1% pet), diethylthiourea (DETU) (1.0% pet), dibutylthiourea (DBTU) (1.0% pet) and diphenylthiourea (DPTU) (1.0% pet). The Shoe series included DETU (1.0% pet), DBTU (1.0% pet) and DPTU (1.0% pet). Patients 1, 2, 6 and 7 were additionally tested with ethylenethiourea (ETU) (1.0% pet), dimethylthiourea (DMTU) (1.0% pet) and trimethylthiourea (TMTU) (1.0% pet). The ETU and DMTU preparations were purchased from Acros Organics and the TMTU preparation was purchased from TCI. Three of the patients were tested with a patch from the suit or cuff (as is) (patient 2, 4 and 5). One patient was also tested with extractions (acetone) from a cuff and an orthopaedic knee brace (patient 5). The study was approved by the Regional Committee for Medical and Health Research (ID10441).

All three patients with isolated leisure exposure (patients 1–3) presented dermatitis on feet and/or ankles (Table 1) (Figure 1). In addition, the patient who had used a kayak paddling dry suit (patient 1) had dermatitis affecting wrists and neck, while the patient who had used wet suits, diving socks and goggles (patient 2) presented dermatitis localised to truncus and arms as well as periorbital oedema and erythema. The patient who had used a weight vest (patient 3) had truncal dermatitis corresponding to the placement of the vest.

Three of the four patients wearing survival suits (patient 4, 6 and 7) presented dermatitis on wrists and/or arms while one patient (patient 5) showed generalised dermatitis.

All seven patients had positive reactions (+++ or ++) to DETU. The patient wearing a kayak paddling dry suit (patient 1) and the patient who had been wearing a survival suit and a wet suit (patient 7) also had positive reactions (++ or +) to DMTU.

Patient 2 was tested with a patch from the wet suit (as is) with a positive reaction (+++) on D3.

Two of the offshore workers (patient 4 and 5) were tested with a patch from the cuff of the survival suit (as is). Patient 4 had a positive reaction (+++) on D3, while patient 5 had no reaction on the cuff on D4, but had a doubtful reaction (?+) to extraction preparation from the cuff in acetone and a positive reaction (+) to extraction from an orthopaedic knee brace in acetone on D3.

In this report, we present seven cases of ACD caused by contact with polychloroprene materials. All patients had positive patch test reactions when tested with DETU. Two patients had a positive reaction to DMTU.

Thiourea compounds are not considered as strong haptens,¹ however the number of reported cases of ACD due to exposure to thiourea compounds have increased over the past years, and has been found to range from 0.6% to 1.3%.^3-5 Studies have suggested that the compounds may act as prehaptens as they are degraded to isothiocyanates, which are considered as strong sensitizers.^{1, 6} Hence, isothiocyanates may be the primary cause of ACD as a response to contact with polychloroprene materials.

We found that DETU was the allergen with the most prevalent number of positive reactions, which is in accordance with findings by Lippo et al.⁴

ACD is previously described in relation to use of wetsuits and diving suits.^{4, 7, 8} Our case report presents the first groups of cases of ACD after use of survival suits in an occupational setting as well as a case of ACD related to use of a weight vest. ACD of the foot is most commonly caused by rubber chemicals,⁹ and thiourea compounds may be found in different types of footwear, including the foam of shoe insoles.^{4, 9} A polychloroprene weight vest was suspected to be the culprit agent for one of the patients. The weight vest represents new fitness equipment developed to add resistance to work. Further, as demonstrated in previous literature, we found that ACD is an important complication to orthopaedic support.^{7, 10} Unfortunately, we were not able to retrieve information from retailers/producers on available thiourea components and the products were not analysed for content of thiourea components.

This case series illustrates that sensitization to polychloroprene compounds may occur both in occupational settings and during leisure and further demonstrates that awareness regarding new sources of exposure is important.

Written consent was obtained for all seven patients for inclusion in the report.

Kaja Irgens-Hansen: Methodology; investigation; project administration; resources; writing – original draft; writing – review and editing. Bjørg Eli Hollund: Methodology; investigation; writing – review and editing. Hilde Kristin Vindenes: Conceptualization; methodology; investigation; resources; writing – review and editing.

The authors declare no conflicts of interest.