Anaerobic sealants: still a problem today

ARTICLE

Case report

A 21-year-old man complained of a chronic dermatitis of his fingers that he had had for 18 months. The tips of the first, second and third fingers of both hands were affected by hyperkeratotic eczema. Onycholysis was also observed in the same fingers.

The dermatitis improved when he was away from work, and promptly relapsed a few days after his return. His work duties included the use of anaerobic sealants for sealing hydraulic cylindrical parts. According to the ICDRG recommendations, patch tests were performed with the Italian GIRDCA series. They were read at 48 and 72 hours and showed only a non-relevant positivity to thimerosal (+ 48 hrs/+ 72 hrs). Further patch tests were performed with the two anaerobic sealants he used (Loctite 500^® and Omnifit H 100^®); both gave a + 48 hours/+ 72 hours positive reaction to the 1% pet concentration while a ++ 48 hours/++ 72 hours reaction was observed with the 5% pet concentration. Supplementary patch tests using the acrylates series showed a positivity to ethylene glycol dimethacrylate (+ 48 hrs/+ 72 hrs) and triethylene glycol dimethacrylate (+ 48 hrs/+ 72 hrs) (Table I). The technical data sheet confirmed that polyethylene glycol dimethacrylate was the principal component of the anaerobic sealant Loctite 500 (over 60%).

Unfortunately the components of the other glue could not be verified due to an ambiguous declaration regarding its composition.

The patient's eczema cleared with a topical corticosteroid treatment while avoiding the use of anaerobic sealants.

Discussion

Anaerobic sealants are liquid adhesives that quickly polymerize and solidify, at room temperature and in the absence of air, when two metallic surfaces are tightly joined together.

The principal constituents of these sealants are dimethacrylates, well known strong sensitizers; stabilizers, accelerators and other additives, like hydroquinone derivatives, are added to improve the products [1, 2].

Anaerobic sealants are widely used in engineering and electronic industries and their use requires particular manual skills as the parts that have to be sealed together are often of small dimensions. This does not allow the use of protective gloves and may well explain the typical clinical pattern of allergic contact dermatitis from anaerobic sealants. The clinical pattern is known to be: redness, hyperkeratosis, scaling and onycholysis of the first three fingers [2].

About 70 cases of allergic contact dermatitis due to anaerobic sealants have been described in literature in the period 1967-1989 [1-5]; Condè-Salazar et al. and Jansen, studying small groups of workers in different factories, reported a rate of prevalence varying from 5 to 12% [2, 4]. In a study performed in Italy in 1993 the prevalence of sensibilization to acrylates was found to be 13.4%; however only two patients had sensitization to anaerobic sealants [6]. Given the widespread use of anaerobic sealants in industry and in domestic and recreational activities, we were surprised not to find new cases reported in recent literature. Some speculative considerations could be raised: is sensitization to anaerobic sealants now considered not worthwhile studying or has sensitization really decreased over the last few years? Perhaps allergies to anaerobic sealants are traceable in different reports which either study various occupational activities or use different batteries of allergens which do not test the same acrylates.

Recently Kanerva et al. and Tarvainen have performed patch-tests with plastic and glue series in a large number of patients but observed a very low percentage of allergies to acrylates [7, 8]. Wide batteries of allergens were used in these studies but only a few acrylates were included: methyl methacrylate, triethylene glycol dimethacrylate or triethylene glycol diacrylate. Kanerva specified that separate patch-test series had been used to study suspected allergies to acrylic resins, in particular in dental personnel [7]. It thus appears difficult to pinpoint the frequency of allergy to acrylic anaerobic sealants in their studies.

Our patient was sensitized to ethylene glycol dimethacrylate and triethylene glycol dimethacrylate; he was not allergic to methyl methacrylate (Fig. 1). Lack of cross-reactivity between methyl methacrylate and polyethylene glycol dimethacrylate is well documented [1, 2, 9]; therefore methyl methacrylate cannot be considered an adequate screen for acrylates. The use of a series of standardized acrylate-allergens is recommended to detect sensitivities to acrylic sealants and to reduce the risk of inducing active sensitization due to performing tests with the patient's own substances.

Our experience underlines the need to improve the material safety data sheet of acrylic sealants as emphasized by Kanerva et al. [10]. We could not, in fact, obtain any information regarding the composition of the Omnifit sealant. This would make it difficult to diagnose and prevent occupational dermatosis due to this product.

Article accepted on 27/4/00

REFERENCES

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