The allergenicity of glycerol esters and other esters of rosin (colophony)

To investigate whether esterification of rosin with polyalcohols changes its allergenic potential. abietic acid, the main component of rosin, was esterified with glycerol at high temperature. The major product formed was isolated and identified, using nuclear magnetic resonance (NMR). infra-red IR) and mass spectrometry (MS) analyses, as glyceryl triabietate (GTA), an ester between one glycerol molecule and 3 abietic acid molecules. According to animal experiments GTA was not allergenic and no cross-reactivity was seen to allergens in unmodified rosin, when testing patients allergic to unmodified rosin, no reactions were found to GTA. Some of the patients reacted to glycerol- and pentaerythritol-esterified rosins. According to HPLC analyses, these esterified rosins still contained unmodified material to which the patients may have reacted. It seems that the esterification of rosin with poly alcohols such as glycerol reduces its allergenic activity, possibly because of the formation of much larger molecules with reduced bioavailability. However, making methyl esters of rosin causes little alteration in the molecular weights of the components and. when unmodified and methylated rosin were tested in patients, we saw no difference between the 2 forms.     

Patch testing with allergens from modified rosin (colophony) discloses additional cases of contact allergy

Most rosin (colophony) used today is chemically modified. Will contact allergy 10 modified rosin be overlooked when testing is performed with only unmodified rosin in the standard series? 2 components from modified rosins. maleopimaric acid (MPA) and glyceryl 1-monoahietale (GMA), earlier identified us contact allergens, were added to the patch lest standard series. Some commonly-used modified rosin products were also tested. Positive reactions were observed to the modified components MPA and GMA. Of the patients with positive reactions to MPA and GMA. several did not react to unmodified rosin in the standard series. No reaction was observed to the modified rosin products without a concomitant reaction to unmodified rosin. The positive reactions observed to the modified rosins may be due to residual unmodified material in the product, but a possible contribution from allergenic modified rosin components cannot be disregarded. When u patient's history indicates a rosin allergy, but a negative response to unmodified rosin in the standard series is observed, additional testing with GMA and MPA or, second best, with glycerol-esterified rosin and maleic-anhydride-modified rosin is recommended. Some modified rosin products, which could be used for additional testing, are suggested.     

Oxidation of resin acids in colophony (rosin) and its implications for patch testing

Commercial preparations of colophony (rosin) used for patch testing are made from unmodified rosin in pet. and may be stored for some considerable time before being used. This would be satisfactory if the composition and dermatological activity of the preparations were both reproducible and stable, but investigations by the authors have shown that the resin acids undergo progressive and substantial oxidation and that the dermatological activity of the preparations increases significantly with time. This may be a cause of inconsistent patch test results unless the composition can be stabilized. Gas liquid chromatography (GLC) analysis of a raw rosin sample and its commercial patch test preparation has shown that they both contained the same resin acids, but the concentration of the abietic type resin acids was found to be lower in the patch test preparations. The degradation of resin acids is due to their atmospheric oxidation, which may occur during the preparation and storage of the commercial rosin patch test preparation. The susceptibility of individual resin acids to atmospheric oxidation was demonstrated by analysing a sample of raw Portuguese gum rosin, which was then left exposed to air and light. Most of the resin acids were found to undergo oxidation at a rate which gradually diminished. More importantly, it is presumed that the concentration of oxidized resin acids increased correspondingly, and these have been shown to be more dermatologically active than the unoxidised resin acids. The rate of decrease of resin acid concentration was found to be in the following order: neoabietic > levopimaric and palustric > abietic > dehydroabetic acid. The pimaric type resin acids were found to be relatively inert to atmospheric oxidation when compared with the abietic type resin acids. Patch testing with the resulting partly oxidized Portuguese rosin produced positive reactions at a 35% higher frequency than the raw Portuguese rosin. The study demonstrates that the allergic potential of unmodified rosin may increase with exposure to air and light. It is therefore recommended that rosin preparations are analysed routinely as part of a quality control programme, which will enable better validation and comparison of patch test results from different dermatological centres. Since the oxidized resin acids are the main allergens in unmodified rosin, it is important that the concentration of the oxidized resin acids is kept high as well as constant in commercial patch test preparations.     

Hydrogenation reduces the allergenicity of colophony (rosin)

Abietic acid is the main component of rosin. It is readily oxidized by air and its oxidation products are considered to be mainly responsible for the allergenic effect. Hydrogenation of the conjugated double bonds of abietic acid decreases its susceptibility to air oxidation and would thus reduce the allergenicity of rosin. Portuguese gum rosin was therefore hydrogenated and its allergenicity was compared with that of unmodified rosin in animal experiments and by patch testing in humans. Its sensitizing potential was determined in 2 studies. No response was found according to the FCAT method while the GPMT gave significant response in the animals challenged with the highest test concentration. Hydrogenated rosin showed no eliciting activity in animals induced with unmodified rosin according to the GPMT method. A marked decrease was found in the frequency of allergic reactions to hydrogenated rosin compared to the reactions to unmodified rosin in patients with known allergy to gum rosin. We conclude that elimination of the unsaturated non-aromatic compounds by hydrogenation considerably reduces the allergenicity of Portuguese gum rosin.     

Detection of rosin (colophony) components in technical products using an HPLC technique

A method for detection of rosin (colophony) in technical products has been developed. The technique, using HPLC, is based on the analysis of abietic acid and dehydroabietic acid, major components of rosin. In the procedure described in this paper, the limit of detection was 0.001% for abietic acid and 0.015% for dehydroabietic acid. An average recovery of 88.9% for abietic acid and 88.2% for dehydroabietic acid was obtained. The lowest detectable amount of abietic acid (0.001%) corresponds to a content of 0.003% unmodified rosin in the product, assuming that the resin acid content in rosin is 90%, of which 30-50% is abietic acid. This is an acceptable limit compared to the reactivity in patients with known allergy to rosin. Technical products for analysis were supplied by different Swedish manufacturers, who also gave the approximate content of rosin in the various products. The content of rosin determined in the products was in accordance with the contents given by the manufacturers.     

Sodium tetrachloropalladate (Na2[PdCl4]) as an improved test salt for palladium allergy patch testing

Background:  In the last decades, palladium is widely used in dentistry. Allergic reactions to palladium are rarely diagnosed with patch testing, even when positive results would be expected. Palladium tends to cross-react with nickel, which should give rise to more positive reactions to palladium dichloride (standard test salt).
Objective:  The aim of the study was to test whether or not mono-nuclear sodium tetrachloropalladate (Na₂[PdCl₄]) in petrolatum is a better test salt for diagnosing palladium allergy. Positive reactions to the investigated test salt are compared not only with PdCl_2(aq.), but also to NiSO_4(aq.) and NiSO_4(pet.).
Patients/Methods:  Concentration series of Na₂[PdCl₄] were carried out. 164 consecutive patients were patch tested.
Results:  3% of Na₂[PdCl₄]_(pet.) was found to be the highest non-irritative concentration. The results show ( n  = 164) that Na₂[PdCl₄] covers all reactions to PdCl₂ (1.8%) and provokes more positive reactions (14%). From the 164 patients, 18.3% reacted positively to at least 1 of the nickel salts.
Conclusion:  The sensitivity of patch testing with Na₂[PdCl₄] is increased compared with the PdCl₂ salt. Therefore, it can be concluded that Na₂[PdCl₄] is to be a better test salt for diagnosing palladium allergy with patch testing.     

Maleopimaric acid – a potent sensitizer in modified rosin

The allergenicity of the maleic-modified rosins and their esters has been studied. The unesterified resins are mainly used in paper size and the esters in printing inks, varnishes and adhesives. The levopimaric-maleic anhydride Diels-Alder adduct (maleopimaric acid) is the main component obtained in the maleic-modified rosins. This compound was synthesized and its structure was determined. Its sensitizing potential was investigated in guinea pigs according to different methods. It was shown that maleopimaric acid is a very potent sensitizer, comparable with the strongest allergen isolated from unmodified gum rosin. The allergen may also be present after esterification unless the process is carried out to completion. The animals sensitized to maleopimaric acid did not react to unmodified rosin, which shows that maleopimaric acid is structurally different from the allergens in rosin.     

Rosin (colophony) and zinc oxide in adhesive bandages

Adhesives and bandages containing zinc oxide (ZnO) and rosin are often used for treatment of ulcers. The aim of this work was to study a possible inhibitory effect of ZnO on the eliciting of allergic contact reactions to rosin und lo determine whether such an effect might be due to the formation of zinc resinates. Patch testing in rosin-sensitive patients was performed with mixes of ZnO and rosin. The eliciting capacities of one mix in which zinc resinates might be formed and another mix in which the formation of zinc resinates was prevented, were compared to the eliciting capacity of rosin alone. If a reduction of the allergic response was observed for the mix in which zinc resinates might form and if no reduction was observed for the mix in which formation of zinc resinates was prevented, this would support the hypothesis that the reduction in eliciting capacity was due to formation of zinc resinates. However, we could not see any difference in eliciting capacity when comparing the 2 mixes with a lest preparation of rosin. Commercial adhesives (bandages) containing ZnO and rosin were patch tested in 7 rosin-sensitive patients. The concentration of abietic acid in the adhesives was determined with HPLC. Abietic acid was detected in all but one of those declared to contain rosin. The patients reacted to the adhesives in which abietic acid was detected. For rosin-sensitive persons, the addition of ZnO to rosin-containing adhesives cannot be regarded as an appropriate measure to inhibit the elicitation of allergic reactions.     

Identification of contact allergens in unmodified rosin using a combination of patch testing and analytical chemistry techniques

Summary In order lo investigate the contact allergens in the unmodified colophony (rosin) used in routine patch testing, preparative chromatographic techniques were used to separate its components which were then patch tested on colophony-sensitive individuals. The chemical structure of the dermatologically active components was elucidated using mass spectrometry, nuclear magnetic resonance and infra-red techniques. The study shows that oxidized resin acids are stronger sensitizers than the resin acids themselves, the most potent contact allergen being 7-oxydehydroahietic acid (purity 92%). At naturally occurring concentrations (relative to abietic acid) all unoxidized resin acids were found to play an insignificant part, individually, in colophony dermatitis, except abietic acid (purity 99%), which was found to be a weak but important allergen. The commercial Trolab abietic acid preparation (unknown purity) was found to be dermatologically more active than purified abietic acid.     

Contact allergy to dehydroabietic acid derivatives isolated from Portuguese colophony

7-oxodehydroabietic acid and 15-hydroxydehydroabietic acid were isolated as their methyl esters from Portuguese colophony of the gum rosin type and identified as contact allergens. Another oxidation product of dehydroabietic acid, 15-hydroxy-7-oxodehydroabietic acid, was synthesized and identified as a component of Portuguese gum rosin. 7-oxodehydroabietic acid was found to a be a grade III allergen according to the GPMT method. Guinea pigs induced with gum rosin showed only a low response to the isolated compounds, while patients with a known allergy to gum rosin reacted to a greater extent. The results imply that the content of oxidized dehydroabietic acids in gum rosin is too low to give a marked sensitization in the animals. However, the patients might have come in contact with the allergens in technically modified rosins. The compounds showed a pattern of cross-reactivity in the animal experiments as well as among the patch tested patients.     

Patch test results with serial dilutions of nickel sulfate (with and without detergent), palladium chloride, and nickel and palladium metal plates

Clinical experience suggests the existence of different degrees of sensitivity in nickel-allergic patients. For quantification of this phenomenon, 462 consecutive patients with previously diagnosed or strongly suspected nickel allergy were tested with serial dilution patch tests with 5 ppm to 5% nickel sulfate in pet. (Ni), and 5 ppm to 1% nickel sulfate in pet. with 1% detergent (Ni/D). Additionally, nickel and palladium metal plates were tested in 103, and cobalt salts, dichromate and palladium chloride (PdCl₂) in most patients. 332 patients reacted positively to Ni or Ni/D. The influence of a concomitantly administered detergent was not significant. A significant correlation was found between positive reactions to low concentrations of Ni (or Ni/D), i.e., 0.1% or less ( N =166), and concomitant reactions to nickel metal plates, cobalt salts and PdCl₂ and a history of ear piercing with metal intolerance. The clinical relevance of reactions to PdCl₂ is at present not clear. A subgroup of nickel-allergic patients with "high sensitivity" can be defined. In future studies further addressing the clinical relevance of high versus low sensitivity, patch testing with 0.01, 0.1, 1.0 and 5% nickel sulfate in pet is recommended instead of routine tests with 5% only.     

A case of contact dermatitis due to impurities of cetyl alcohol

A 29-year-old man being treated for itchy lesions on the amputation stump of the thigh became allergic to betamethasone valerate and gentamicin sulfate cream (Rinderon VG®. Closed patch tests with all the ingredients of the cream revealed positive reactions to cetyl alcohol 30% to 5% pet. Gas chromatographic analysis of the cetyl alcohol in the cream base detected stearyl alcohol (C₁₈), myristyl alcohol (C₁₄) and lauryl alcohol (C₁₂) in addition to the main component of cetyl alcohol (C₁₆). Patch testing with 99% pure analytical reagent grade saturated alcohols. (C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅, C₁₆, C₁₇, C₁₈, C₁₉, C₂₀) showed negative reactions. Thus, it is concluded that some minor impurities in cetyl alcohol not detected by gas chromatography might be the cause of this dermatitis.     

Clinical experience and patch testing using colophony (rosin) from different sources

Patients with suspected allergy to colophony were patch-tested with colophony (rosin) of different kinds (gum rosin, tall oil rosin). More cases of allergy were detected by testing with more than one type of colophony. Tall oil rosin produced a smaller number of positive reactions than the gum rosins tested, which suggests a lower allergenic activity. Venice turpentine was a useful additional screening substance. When different test concentrations were compared (20% and 5%) the lower concentration failed to reveal four of 30 cases. The patients' eczema had been caused chiefly by contact with colophony in their work.     

Concentration threshold of non-occluded nickel exposure in nickel-sensitive individuals and controls with and without surfactant

Most cases of primary nickel sensitization are caused by occluded exposure to nickel released from earrings, buttons, etc. Nickel-sensitive females are both domestically and occupationally exposed lo trace amounts of nickel. The present study was designed to define the minimum eliciting threshold concentration of nickel exposure in previously nickel-sensitized individuals, after open application on normal forearm skin with and without surfactant. A dilution series of NiCl₂, ranging from 0.1 to 4000 ppm nickel with and without 4% sodium Lauryl sulfate, was applied to healthy volar forearm skin. None reacted with definite allergic reactions to 100 ppm and below. Follicular reactions were seen in the concentration range from 0.1–100 ppm in a few patients and 1 healthy control. The results are discussed in relation to consumer products containing 1–10 ppm nickel.     

Allergy to phosphorus sesquisulfide: 0.5% pet. is a more appropriate concentration for patch testing

Patch testing was performed with phosphorus sesquisulfide P₄S₃ in 2 groups containing equal numbers of patients using different concentrations (0.5% P₄S₃ in pet. and 1% P₄S₃ in pet., the usual suggested test concentration as recommended by the International Contact Dermatitis Research Group). We found that there was a statistically significant increase in the number of clinically irrelevant irritant reactions in the group tested with the concentration (χ²= 16, P < 0.0004). We recommend that patch testing with phosphorous sesquisulfide should he at a reduced concentration of 0.5% pet.     

Interaction of metals in nickel-sensitive patients

Nickel (Ni) dermatitis is, thought to involve the formation of complexes between Ni ions and suitable proteins. 4 groups of 30 subjects who gave positive patch test responses to NiSO₄ 2.9% aq. were each retested to 1 of 4 different solutions containing equimolar (0.1 M) amounts of NiSO₄ plus MgSO₄. NiSO₄ plus CuSO₄, NiSO₄plus ZnSO₄. and NiSO₄ plus Li₂SO₄, respectively. The results, evaluated at 2 days by visual scoring only, demonstrated that the 4 metals exerted a different influence on the nickel reactions, perhaps interfering with one or more factors affecting the formation of Ni++ complexes.     

Contact allergy due to colophony

Degradation of abietic, levopimaric and dehydroabietic acids after exposure to air and light over a period of one to several months, as well its examination of degraded French tall oil rosin and Portuguese colophony, led to the isolation of numerous oxidation products. These compounds were synthesized and consigned to experimental sensitization in guinea pigs. From 20 substances studied as acids or as their methyl esters, in the present and preceding paper, at least 2 can be named: 8.12-peroxydo-δ¹³⁽¹⁴⁾-dihydroabietic acid and 12 α-hydroxyabietic acid, that contribute a great deal to colophony allergy by both their sensitizing capacity and their determined concentration in the mixture of degradation products. We recommend the preparation of a new mixture oxidation products for patch testing in the diagnosis of contact allergy to colophony.     

Elicitation thresholds for thiuram mix using petrolatum and ethanol/sweat as vehicles

An estimate of amounts of thiurams that may be released from rubber gloves into synthetic sweat, has previously been generated. These amounts should be compared to elicitation thresholds Of patch tests performed with serial dilutions of thiuram mix using synthetic sweat as vehicle. Because of solubility properties of thiurams in aqueous media, such dilutions cannot directly be prepared. In this study, a stem solution was prepared in ethanol. This solution was then further diluted with synthetic sweat. Thiuram mix 0.5 w/v% was the most concentrated solution in ethanol achievable. The parch test reactions were compared to reactions to serial dilutions using petrolatum as vehicle. The experiment revealed that endpoint dilution with synthetic sweat was not achieved in this study. The threshold for elicitation of positive patch test reactions seemed to be lower for ethanol/sweat a, vehicle compared to petrolatum: 32% reacted to ethanol/synthetic sweat 0.001 mg/cm₂ compared to 14% reading to thiuram in pet. 0.0Q2 mg/cm₂. Based on these results, synthetic sweat may be considered a more relevant medium for threshold finding studies than petrolatum. Because of expected instability of the aqueous solutions, petrolatum is probably a more suitable vehicle for routine testing. The study does not permit final conclusions concerning acceptable thresholds for reachable thiurams in rubber gloves, but it is likely that an acceptable threshold would be substantially less than 0001 mg/cm₂.     

Contact allergy due to colophony (VI). The sensitizing capacity of minor resin acids and 7 commercial modified-colophony products

3 minor resin acids and 7 commercial modified-colophony products of different origins were studied by experimental sensitization by means of a modified FCA method. All 3 resin acids were almost negative. The commercial products gave different results. While the maleic-modified product of Greek origin showed a strong sensitizing power, the fumaric-modified, terpene-phenol-modified and a disproportioned rosin were only moderate. A remarkable difference was obtained with the Swedish and Finnish tall oil rosins, which, in contrast to the previously studied French product, exhibited only a weak sensitizing capacity.