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Acid anhydrides are low-molecular-weight chemicals known to cause respiratory irritancy and allergy. Skin allergy has on rare occasions been reported. 2 workers contracted hives and itching on uncovered skin after 2 months exposure to methyltetrahydrophthalic anhydride (MTHPA) and methylhexahydrophthalic anhydride (MHHPA), to which they had airborne exposure. Later, the patients also developed conjunctivitis, rhinitis, sore throat, cough or asthma. In addition to MTHPA, 1 worker was also exposed to unsaturated polyester resin (UP). Both patients' immediate allergy to MTHPA and MHHPA was verified by positive prick tests to MTHPA and MHHPA, conjugated with human serum albumin (HSA), and positive radioallergosorbent tests (RASTs) to these anhydrides. On prick testing, both patients also reacted to a phthalic anhydride (PA)-HSA-conjugate and 1 of the patients to UP-HSA-conjugate. Specific immediate allergy to UP was shown by RAST. RAST inhibition with MTHPA, MHHPA and UP-resin conjugates confirmed IgE-mediated allergy and cross-reactivity between anhydrides. Our patients had developed airborne contact urticaria caused by phthalic anhydrides, in addition to respiratory allergy. Phthalic anhydride contained in the UP resin was possibly responsible for the immediate reaction of the skin.

6 men contracted occupational allergic contact dermatitis from unsaturated polyester (UP) cements. 4 of the men were employed in car repair painting and the remaining 2 in mold manufacturing. The exposure time to UP cements ranged from 6 to 32 years before onset of skin symptoms. All patients had eczema on their hands; in addition, 4 had skin symptoms on airborne areas, i.e., wrists, neck and face. All 6 patients developed allergic reactions when patch tested with UP resin at 0.5-10% in petrolatum (pet.). None of the tested patients reacted to auxiliary or cross-linking chemicals of the cements. Diethylene glycol maleate (DGM) was purified and identified from the UP resin of a cement. 1 patient reacting to UP resin was also patch test positive to DGM and he produced an allergic reaction to DGM down to a concentration of 0.0032% pet. DGM was found in both uncured and cured UP resin. None of the patients could continue their work with UP cements after their sensitization.

In addition to asthma, contact dermatitis may also develop from occupational contact with polyurethane (PU) chemicals. 6 cases of allergic contact dermatitis from exposure to PU chemicals were diagnosed in 1974-1990. The present paper summarizes the results and gives detailed descriptions of 3 such patients. 3 patients were allergic to 5 different diisocyanates (DICs), including 4,4'-diphenylmethane DIC (MDI), toluene DIC (TDI), 1,6-hexamethylene DIC (HID), and furthermore to diaminodiphenylmethane (MDA). 3 patients were sensitized by exposure to MDI. 2 of these reacted to MDI and MDA, and 1 to TDI in addition. 1 of the 3 patients reacted only to MDA, possibly formed by hydrolysis of MDI. Primary sensitization to MDA and cross-allergy to MDI could explain the reactions of the patients exposed to MDI, but separate sensitization may also be possible. Patch tests with fresh petrolatum (pet.) mixtures were first made and a 2% concentration was recommended for MDI and TDI. In order to determine the stability of DIC test substances, the last 2 patients were tested with old test substances. Tests with MDI 1.5% pet. and TDI 1.5% pet., 5.5 months and 15.5 months old, were positive. The results suggest that, when allergy to PU chemicals is suspected, patch tests should include, in addition to MDA, at least MDI and TDI 1.5-2% pet. They also suggest that test substances can be used for over a year, and that allergy to MDA may point to MDI exposure contained in PU chemicals.

This case report presents two patients with immediate and delayed allergy to epoxy resins based on diglycidyl ether of bisphenol A (DGEBA). In patch testing, the epoxy resin (DGEBA-based) of the standard series gave allergic reactions. Both patients had a prick test reaction of histamine size or larger to the human serum albumin (HSA) conjugate of DGEBA-based epoxy resins. One had been occupationally exposed to methyl tetrahydrophthalic anhydride (MTHPA) and had a histamine-size prick test reaction to the HSA conjugate of MTHPA; the other did not react to the conjugate. Determinations of specific immunoglobulin E were carried out with HSA-DGEBA conjugates, two DGEBA-based epoxy resins, and phthalic anhydrides. The first patient had positive tests to DGEBA, the DGEBA-based epoxy resins, and two phthalic anhydrides, and the second to DGEBA and the DGEBA-based epoxy resins, but not to the phthalic anhydrides.

This study comprises 40 patients with skin disorders from current or previous occupational exposure to epoxy resin compounds (ERC) during 1984-1988. ERCs were the 3rd most common cause (32 of 264 cases: 12.1%) of currently relevant allergic contact dermatitis: 23 cases from epoxy resins based on the diglycidyl ether of bisphenol A (DGEBA-ERs), 5 from reactive diluents, 1 from amine hardeners (DETA), and 3 from epoxy acrylates. 2 cases (0.8%) of irritant contact dermatitis were due to ERCs. Methyl hexahydrophthalic anhydride (MHHPA, an epoxy hardener) caused 1 case of contact urticaria. Previously relevant occupational allergic contact dermatitis from DGEBA-ERs was detected in 5 cases. On patch testing, ERC allergens gave the following positive reactions: epoxy resin of the standard series in 35 cases (4.0% of 870 tested), epoxy reactive diluents in 10 (7.1% of 140), cycloaliphatic epoxy resins in 4 (11.1% of 36), epoxy acrylates in 4 (4.5% of 88), and amine compounds commonly used as epoxy hardeners in 17. Despite extensive patch test series, testing with patients' own ERCs remains important.

Between 1974 and 1992, we were consulted by 4 patients (an orthodontist, 2 dental technicians and a dental worker trained in-house) who had developed occupational allergic contact dermatitis from working with dental prostheses. All patients had positive allergic patch test reactions to methyl methacrylate (MMA), the acrylate which is the most widely used in work with prostheses. All but the orthodontist also reacted to dimethacrylates, which are used in cross-linked dental prostheses. The last patient, investigated in 1992, had been exposed mainly to light-cured acrylics, which are similar in composition to dental composite resins. These acrylics, only recently introduced into prosthetic work, contain more potent acrylic sensitizers than MMA. Accordingly, dental personnel working with prostheses may face a higher risk of sensitization than previously. To detect cases of occupational allergic contact dermatitis, we suggest that patients working with dental prostheses should be patch tested with MMA, 2-hydroxyethyl methacrylate, dimethacrylates, epoxy acrylates and urethane acrylates.