Patterns of simultaneous contact allergies in patients with contact sensitization to oxidised linalool and oxidised limonene.

BACKGROUND: Contact allergy rates of linalool and limonene hydroperoxides (HPs) have increased. OBJECTIVES: To demonstrate the patterns of simultaneous positive patch test (PT) reactions and prevalences of multiple contact allergies (MCAs) in patients with contact allergy to linalool and/or limonene HPs. METHODS: A retrospective analysis of consecutive dermatitis patients in 2015-2020 was performed. RESULTS: Of all 4192 patients, 1851 had at least one positive PT reaction. Of these, 410 (22.2%) had MCAs, significantly related to a higher age (p-value = 0.003). Patients with an exclusively positive reaction to linalool HPs but not limonene HPs were shown to have MCAs (p-value <0.001, odds ratio (95% confidence interval) = 4.15 (3.01-5.73)). Patients with simultaneous contact allergies to both linalool and limonene HPs had contact allergies to many other screening and fragrance allergens. CONCLUSIONS: Simultaneous positive PT reactions to allergens in baseline series and fragrances are common in patients with the HPs contact allergy, especially linalool HPs. The pattern of simultaneous PT reactions principally suggested the co-sensitization of the cosmetic allergens.

Allergic contact dermatitis due to 1,6-hexanediol diacrylate in ostomy patients.

BACKGROUND: Many people live with ostomies after life-saving surgery. Ostomy patients often suffer from peristomal dermatitis. Allergic contact dermatitis (ACD) has been reported, mostly due to contact allergy (CA) to topical agents. OBJECTIVES: We present three patients with therapy resistant peristomal dermatitis, suggesting ACD caused by different stoma products. METHODS: Patch testing was performed with baseline series, additional series, and selected allergens. They were also tested with their own ostomy products as is and separate extracts of the products. Extracts were analysed using Gas Chromatography-Mass Spectrometry (GC-MS). RESULTS: In all three patients we diagnosed CA to 1,6-hexanediol diacrylate (HDDA), +++ in case (C) 1 and 3, ++ in C 2. HDDA was detected in C 2's ostomy pouch adhesive and in C 1's and 3's flange extenders used to improve the adhesion of the ostomy pouches. CONCLUSION: Therapy resistant peristomal dermatitis should always be suspected of ACD and patch testing, especially with the patient's own products, should be performed.

Oral lichenoid lesions in two snuff users with contact allergy to carvone.

BACKGROUND: Contact allergy to the mint-tasting flavour carvone has been observed in patients with oral lichenoid lesions (OLL). Mint-flavoured products such as toothpaste frequently contain carvone. Snuff is a smokeless tobacco product that is chewed or placed in the mouth rather than smoked. In Sweden, the use of snuff and its flavoured versions is extremely common. OBJECTIVES: To investigate whether the consumption of mint-flavoured snuff is associated with contact allergy to carvone and subsequently plays a role in the aetiology of OLL. METHODS: Regarding the two patients, patch testing with snuff pouches was performed. High-performance liquid chromatography and gas chromatography-mass spectrometry analysis were used for identification of carvone in different snuff samples. RESULTS: Two patients with OLL were contacted allergic to carvone when patch tested. Both were using mint-flavoured snuffs several hours a day for many years. One patient was contacted allergic to the snuff pouch tested as is. Carvone was detected in the snuff samples of both patients. CONCLUSIONS: The patients were recommended to avoid the use of mint-flavoured snuffs, toothpaste and foodstuffs. At follow-up 3 months later, the patients had a dramatic clinical improvement of the OLL and oral symptoms. Exposure to mint-flavoured snuffs can be overlooked as a possible aggravating/provoking factor in OLL.

Contact allergy in Swedish professional ice hockey players.

BACKGROUND: Professional ice hockey players may contract irritant and allergic contact dermatitis. AIMS: To investigate the presence of contact allergy (CA) in professional ice hockey players in Sweden. METHODS: Ten teams from the two top leagues were assessed for potential occupational exposure to sensitizers. Exactly 107 players were patch tested with an extended baseline series and a working series, in total 74 test preparations. The CA rates were compared between the ice hockey players and controls from the general population and dermatitis patients. RESULTS: One out of 4 players had at least one contact allergy. The most common sensitizers were Amerchol L 101, nickel and oxidized limonene. CA was as common in the ice hockey players as in dermatitis patients and significantly more common than in the general population. Fragrances and combined sensitizers in cosmetic products (fragrances + preservatives + emulsifier) were significantly more common in ice hockey players compared with the general population. CONCLUSION: The possible relationship between CA to fragrances and cosmetic products on the one hand and the presence of dermatitis on the other should be explored further.

Colophonium-related Allergic Contact Dermatitis Caused by Medical Adhesive Tape Used to Prevent Skin Lesions in Soldiers.

Medical adhesive tapes are commonly recommended for the prevention of friction blisters during hiking and military marches. The aim of this paper is to report on the results of investigations into an outbreak of tape-related foot dermatitis in 26 military conscripts following continuous use of medical adhesive tapes for several days during a field exercise. Patch tests were performed using baseline series and aimed testing was performed with colophonium-related substances and different medical adhesive tapes. Contact allergy to the adhesive tapes used was found in 20 (77%) subjects, and contact allergy to colophonium in 16 (61%). Chemical analysis detected colophonium-related substances in the culprit tapes. Compared with consecutive dermatitis patients investigated at our Department of Occupational and Environmental Dermatology in the previous 10 years, conscripts with colophonium allergy had increased odds ratios for concomitant contact allergy to phenol formaldehyde resins and fragrance substances including hydroperoxides of limonene and linalool. The results show that prolonged use of medical adhesive tapes on intact skin carries a high risk for allergic contact dermatitis. Prior to their introduction on the market, medical devices should be assessed for possible side-effects.

Increased Rates of Gold and Acrylate Allergy in Individuals with Fibromyalgia Tested with an Extended Dental Patch Test Series.

Fibromyalgia is a common chronic pain condition. Rates of contact allergy in individuals with fibromyalgia have not been widely studied. Systemic contact allergy can present with muscle and joint pain and general malaise. The aim of this study is to investigate contact allergy rates in individuals with fibromyalgia to the sensitizers in an extended dental series and compare with control groups. Contact allergy to gold was significantly more common in the fibromyalgia group than the dermatitis control group. When corrected for patch test system, contact allergy to gold was significantly more common in the fibromyalgia group than the dental control group. Contact allergy to hydroxyethyl methacrylate and grouped acrylates and methacrylates was significantly more common in the fibromyalgia group than the dental control group. In conclusion, individuals with fibromyalgia may have a propensity to sensitization to gold, either via an increased exposure or an alteration in the oral environment. Gold is also implicated in systemic contact dermatitis and may be a factor in elicitation of symptoms in individuals with fibromyalgia. Acrylate allergy is also common in the fibromyalgia population and may be a consequence of occupational exposure or dental treatment.

Increased rates of fragrance allergy in fibromyalgia individuals tested with the Swedish baseline patch test series.

BACKGROUND: Contact allergy can manifest in a variety of ways clinically. Systemic contact allergy may occasionally present with pain in muscles and joints. Fibromyalgia is a chronic rheumatic disease characterized by pain and with virtually unknown aetiology. OBJECTIVES: The aim of this study was to investigate the contact allergy rates to the sensitizers in a baseline series and compare with corresponding rates in dermatitis patients and the general population. METHODS: Patch testing with the Swedish baseline series was performed in 120 individuals with fibromyalgia. Fisher's exact test was used for pair-wise comparisons of contact allergy rates between the fibromyalgia group and two control groups, dermatitis patients and individuals in the general population. RESULTS: Contact allergy was significantly more common in the fibromyalgia group compared to the general population concerning nickel and the fragrance markers Myroxolon pereirae and fragrance mix I. There were fewer allergic reactions to preservatives in the fibromyalgia group compared with the dermatitis group. CONCLUSIONS: Myroxolon pereirae and fragrance mix I represent besides fragrance allergy also allergy to flavouring substances which indicate that oral exposure to flavouring substances and hygiene products might be important for sensitization and possibly elicitation of systemic contact allergy symptoms in fibromyalgia individuals.

Effects of aluminium chloride added to common patch test substances.

BACKGROUND: A modulating effect of aluminium regarding type IV reactions might exist but has not been further investigated. OBJECTIVES: The aim of this study was to investigate the effect on patch test reactions when adding aluminium chloride hexahydrate (Al-Cl) to common test preparations. MATERIALS AND METHODS: Al-Cl in different concentrations was added to nickel sulphate 15.0% aqua (Ni), methylisothiazolinone 0.2% aqua (MI) and fragrance mix I 10.0% aqua/ethanol (FM I). The Ni preparations were tested in 120 consecutive patients. MI and FM I were tested in participants known to have contact allergy to the respective allergen. McNemar's test was used to decide which Ni preparation had the highest sensitivity. Wilcoxon signed-rank test was used to calculate pairwise comparison in summarized test score for the preparations with MI and FM I. RESULTS: Adding Al-Cl 20.0%/30.0% to Ni identified twice as many patients with contact allergy to nickel compared to Ni without Al-Cl. Adding Al-Cl 20.0%/10.0% to MI, decreased the patch test reactivity compared to MI without Al-Cl. No differences in patch reactivity were noticed when adding Al-Cl to FM I. CONCLUSION: Al-Cl 20.0% or 30.0% seems to enhance the patch test reactivity to Ni 15.0% aqua.

4,4'-Thiobis(2-tert-butyl-5-methylphenol), an antioxidant in medical devices that may cause allergic contact dermatitis.

BACKGROUND: Antioxidants in medical devices, added to protect polymers or adhesives, may also cause contact dermatitis in some individuals. OBJECTIVES: To present data on sensitization to 4,4'-thiobis(2-tert-butyl-5-methylphenol), an antioxidant detected in some types of medical devices, for six patients that experienced eczematous reactions to different medical devices. METHODS: Patch testing with 4,4'-thiobis(2-tert-butyl-5-methylphenol), 1% pet was performed. Gas chromatography-mass spectrometry (GC-MS) was used for identification of 4,4'-thiobis(2-tert-butyl-5-methylphenol) in different medical device products. RESULTS: Six patients with contact allergy to 4,4'-thiobis(2-tert-butyl-5-methylphenol) also had relevant contact allergic reactions to medical devices containing the antioxidant. The presence of the antioxidant in products was detected using GC-MS analysis. CONCLUSIONS: The antioxidant 4,4'-thiobis(2-tert-butyl-5-methylphenol) may cause allergic contact dermatitis after exposure to different medical devices.

Use test with l-carvone in toothpaste on sensitized individuals.

BACKGROUND: The mint flavour carvone (l-carvone) is considered a weak contact allergen. However, contact allergy to carvone is more prevalent in patients with oral lichen planus or oral lichenoid lesions (OLP/OLL). OBJECTIVE: Our aim was to investigate how carvone affects sensitized individuals through a use test with toothpaste containing carvone. Non-flavoured toothpaste served as control. METHODS: Subjects were patch tested prior to the use test-14 subjects allergic to carvone (11 with OLP/OLL), 20 subjects with OLP/OLL and 3 healthy controls. The month-long use test comprised of using toothpaste twice daily. Subjects were examined fortnightly. Clinical signs were assessed with a mucosal scoring system. The subjects' oral health-related quality of life was measured with the oral health impact profile (OHIP-49). RESULTS: Local reactions to the carvone toothpaste presented as aggravated OLL (7/10) and peri-oral eczema (2/10) in allergic subjects. They also had significantly higher mucosal and OHIP scores compared with those receiving non-flavoured toothpaste. CONCLUSION: In sensitized individuals, oral exposure to carvone gives aggravated oral lesions and/or peri-oral eczema. The lesions mimic OLP and allergic individuals are therefore at risk of not being assessed with regard to flavour contact allergy.

Exclusion of Disperse Orange 3 is possible from the textile dye mix present in the Swedish baseline patch test series. A study by the Swedish Contact Dermatitis Research Group.

BACKGROUND: The textile dye mix (TDM) 6.6% in petrolatum contains Disperse Blue (DB) 35, Disperse Yellow 3, Disperse Orange (DO) 1 and 3, Disperse Red 1 and 17, and DB 106 and 124. The most frequent allergen in TDM-positive patients is DO 3. Around 85% of para-phenylenediamine (PPD)-allergic dermatitis patients have been positive to DO 3. There has been a discussion to exclude DO 3 from TDM 6.6% because of strong simultaneous reactions to TDM and PPD. OBJECTIVES: To study if DO 3 can be excluded from TDM 6.6%. METHODS: Patch tests were performed on 1481 dermatitis patients with TDM 6.6%, TDM 7.0% (without DO 3 but the other disperse dyes at 1.0% each), DO 3 1.0%, and PPD 1.0% pet. RESULTS: Contact allergy to TDM 6.6% was 3.6% and to TDM 7.0% was 3.0%. All 26 DO 3-positive patients were positive to PPD. The 44 patients positive to TDM 7.0% plus the 13 positive to PPD and TDM 6.6% but negative to TDM 7.0% were 57, outnumbering the 53 positive to TDM 6.6%. CONCLUSION: TDM 7.0% can replace TDM 6.6% in the Swedish baseline series, since TDM 7.0% together with PPD 1.0% will detect patients with textile dye allergy.

Cosmetic preservative labeling in Philippine products in accordance with Philippine regulations.

BACKGROUND: Preservatives are usually added to a wide array of consumer products to prevent growth of microbes and to prevent product destabilization and degradation. However, many of these preservatives are common skin sensitizers and may cause allergic contact dermatitis. The amount of preservatives may vary per country or region according to their respective legislation and may be reported in differences in prevalence rates of contact dermatitis. OBJECTIVE: To examine and identify preservatives in consumer products in accordance with Philippine legislation. To verify the accuracy of the list of ingredients of Philippine cosmetic products as legislated by the Philippine Bureau of Food and Drug Administration. METHODS: A total of 65 commonly used Philippine consumer products ranging from liquid facial and body washes, bar soaps, laundry detergents, feminine hygiene washes and wipes, shampoos and conditioners, sunblock, and moisturizers were selected. Ingredients noted on labels were documented. Products were subsequently investigated chemically for the presence of methylchloroisothiazolinone, methylisothiazolinone, or formaldehyde. RESULTS: The preservatives most commonly used in cosmetic products in the Philippine market are methylchloroisothiazolinone (MCI), methylisothiazolinone (MI), and/or formaldehyde. In accordance with Philippine legislation, almost all products provided a detailed ingredient list as printed on the packaging. Measurements of MCI/MI ranged from less than 1 ppm to 16 ppm, and MI ranged from only less than 1 ppm to 66 ppm, whereas formaldehyde was noted to range from less than 2.5 ppm to greater than 40 ppm in the products tested. Most products are manufactured by international brands, with a few products being manufactured locally. CONCLUSIONS: The preservatives found in cosmetic products were MCI, MI, and formaldehyde. Discrepancies were found in the preservatives and labeling of these products, with a majority of investigated Philippine products labeled inaccurately with varying concentrations of preservatives.

Allergic contact dermatitis from dyes used in the temple of spectacles.

BACKGROUND: We observed an increasing number of patients who presented with facial or retro-auricular dermatitis after skin contact with plastic spectacles or plastic covered temples. OBJECTIVES: To identify the allergens in plastic spectacles that may cause allergic contact dermatitis. METHODS: All patients with suspected allergic contact dermatitis to eyewear were tested with Solvent Orange 60 (SO60), four additionally with Solvent Yellow 14 (SY14), and five with scrapings from their own spectacles. In one case, a chemical analysis of the spectacles was performed to uncover the causative allergen. RESULTS: Three patients were allergic to SO60, two patients to SY14, and two patients were allergic to both SO60 and SY14. CONCLUSION: Patients with suspected allergic contact dermatitis from spectacles should be tested with SO60 and SY14, and based on findings from previous reports, also with Solvent Red 179.

Simultaneous patch testing with fragrance markers in the baseline series and the ingredients of fragrance mixes: An update from southern Sweden.

BACKGROUND: Regularly updating the prevalence of fragrance contact allergy (CA) is important. Patch testing with fragrance markers in the baseline series and the ingredients of fragrance mixes (FMs) is still debated. OBJECTIVES: To update the prevalence and clinical characteristics of patients with fragrance CA. To establish the results of patch testing with individual allergens of FMs. METHODS: A retrospective analysis of 3539 patients with dermatitis who were patch tested with the baseline series and FMs ingredients during 2016 to 2020 was performed. RESULTS: The prevalence of fragrance CA was 13%. About 10% of these patients with fragrance CA would be missed if the individual ingredients were not tested. Unlike hydroxyisohexyl 3-cyclohexene carboxaldehyde, there was no decreasing trend of CA to Evernia prunastri (oakmoss) extract after the EU regulation came into force. Patients with CA from only one ingredient of the mixes or having a weak positive reaction to the ingredients were significantly missed when tested with only the fragrance markers in the baseline series. CONCLUSIONS: Patch testing with individual fragrance allergens is crucial for experts to expand knowledge in the fragrance CA field. The concentrations of the allergens in FMs may need to be adjusted to detect patients with fragrance CA, since some were significantly overlooked.

Patch test results to extracts of synthetic garments in textile dye positive patients.

BACKGROUND: Disperse dyes (DDs) are the most prevalent causes of textile-related allergic contact dermatitis and are used for colouring synthetic textile materials based on fibres such as polyester, acrylic, acetate and polyamide. Eight DDs are included in a textile dye mix (TDM) 6.6% petrolatum (pet.) in the European baseline patch test series. OBJECTIVES: The aim of this study was to patch test TDM 6.6% pet. positive individuals with the extracts of synthetic fibre clothes that do not contain any of the pure DDs present in the TDM 6.6% to study the reactivity pattern. METHODS: Seventy-three TDM-positive former patients tested between 2012 and 2017 at the Department of Occupational and Environmental Dermatology in Malmö, Sweden were invited to join the study, 10 participated. Twenty-four textile items (collected in nine countries in Europe, Asia and North America in 2012) were extracted in dichloromethane. The TDM 6.6% was patch tested simultaneously with the 24 textile item preparations in petrolatum made from the extracts. Prior to patch testing the participants filled the 7-question questionnaire regarding possible symptoms from textile exposure. RESULTS: Ten individuals, agreed to join the study. Eight of them reacted to TDM 6.6%. Nine participants reacted to 20 of 24 extracts. One reacted to 19 extracts, another to 14, 3 to 5 extracts, 1 to 4, 1 to 3 extracts and 2 to 2 extracts. One was negative to all tested preparations including TDM 6.6%. The participants mainly reacted to six textile extracts. All controls tested negatively to tested extracts. Four individuals of the 10 TDM-allergic individuals previously had had problems after wearing clothes. Four out of the 10 participants had had atopic eczema in childhood. All women had dyed their hair with permanent hair dyes but none of the males. CONCLUSION: TDM-positive patients react to textile extracts made from synthetic garments, even if they do not contain any of the pure DDs present in TDM 6.6%. More studies are needed to pin-point the culprit haptens in these extracts.

A new case of photoallergic contact dermatitis caused by benzophenones in magazine covers.

BACKGROUND: Allergic contact dermatitis (ACD) and photoallergic contact dermatitis (PACD) to benzophenone present in printing ink have been reported. However, precise chemical analyses and extended photo-patch tests have not been performed in these cases. OBJECTIVES: To determine which components present in a magazine cover are responsible for a patient's skin reaction, to determine the primary sensitizer, and precisely diagnose ACD and PACD. METHODS: After initial photo-patch tests were performed on a patient with a history of reaction to magazine covers after sun exposure, gas chromatography-mass spectrometry and high-performance liquid chromatography analyses of the magazine covers, and additional photo-patch tests were performed. RESULTS: The first photo-patch test results confirmed PACD to ketoprofen and fenofibrate and evoked PACD to the magazine covers. 4-methyl benzophenone (4-MBP) and 1-hydroxy-cyclohexyl-phenyl-ketone (1-HCPK) were found in the magazine cover. Additional photo-patch tests confirmed PACD to 1-HCPK and to benzophenone, and photo-aggravated ACD to 4-MBP. The primary sensitizer was ketoprofen. CONCLUSIONS: Benzophenones are present in a wide variety of products, without always being listed on the packaging. Patients previously sensitized to other ketones, such as ketoprofen, may react to benzophenones without being able to avoid contact with these molecules. New regulations may be needed for more efficient eviction advice.

Contact allergy to oxidized linalool and oxidized limonene: Patch testing in consecutive patients with dermatitis.

BACKGROUND: Contact allergy to oxidized (ox.) linalool and ox. limonene has been reported to have a high prevalence, raising the question of inclusion into the baseline series. However, several important issues should be clarified and further investigated before inclusion can be warranted. OBJECTIVES: To report the trends of ox. terpenes allergy in patients with dermatitis, features of the patch test reactions, and clinical characteristics of the patients. METHODS: A retrospective analysis of 5773 patients was performed. All patients were patch tested with baseline series, individual ingredients of fragrance mix I and II, ox. linalool, and ox. limonene from 2013 to 2020. RESULTS: The prevalence rates of contact allergy to ox. linalool and ox. limonene were 7.0% and 5.1%, respectively. Significantly increasing trends of contact allergy were observed. More than 95% of contact allergy cases were identified on Day 3/4. Patients with contact allergy to ox. linalool and ox. limonene were significantly younger than those with contact allergy to other fragrances and were predominantly female. Strong reactions were associated with older age and multiple fragrance allergies. CONCLUSIONS: Contact allergy to ox. linalool and ox. limonene is becoming increasingly important, and findings show intriguing features. More studies concerning the clinical relevance before recommending these substances for screening are required.

Patch testing with aluminium Finn Chambers could give false-positive reactions in patients with contact allergy to aluminium.

BACKGROUND: Earlier laboratory studies have shown that sodium tetrachloropalladate, Myroxylon pereirae, caine mix II, and palladium chloride trigger the release of aluminium (Al) from Finn Chambers (FC). OBJECTIVES: To investigate whether aluminium realease from FC could influence the diagnostic outcome of patch testing with FC. METHOD: A retrospective analysis of patch test results from 2010 to 2019 was performed. A two-sided Fisher's exact test was used to calculate any overrepresentation of contact allergy to Al among patients with positive reactions to sodium tetrachloropalladate, Myroxylon pereirae, caine mix II, and palladium chloride. RESULTS: A total of 5446 patients had been tested with FC during the study period. There was a significant overrepresentation of contact allergy to Al among patients with positive reactions to sodium tetrachloropalladate, Myroxylon pereirae, caine mix II, and palladium chloride. Patients with a strong Al allergy had significantly higher amounts of concomitant reactions to sodium tetrachloropalladate, Myroxylon pereirae, caine mix II, and palladium chloride compared to patients with weak Al allergy. These results were not seen for patients tested with Finn Chambers AQUA. CONCLUSION: In patients with contact allergy to Al, patch testing with Finn chambers could give false-positive reactions to sodium tetrachloropalladate, Myroxylon pereirae, caine mix II, and palladium chloride.

Bikini textile contact dermatitis: A Sherlockian approach revealing 2,4-dichlorophenol as a potential textile contact allergen.

BACKGROUND: Different textile constituents may act as allergens and/or irritants and provoke textile contact dermatitis (TCD). OBJECTIVES: To report a case of TCD caused by ethylene glycol monododecyl ether and 2,4-dichlorophenol, present in a bikini. METHODS: A woman presented with an eczematous, pruritic rash in the area of the bikini straps and back. Patch testing was performed with the European baseline, textile, sunscreen, and photo-patch series, the bikini "as is", and ethanol and acetone extracts of the bikini. Thin-layer chromatography (TLC) of the extracts and gas chromatography-mass spectrometry (GC-MS) analysis were used to elucidate the culprit agents. RESULTS: Positive reactions were found to the bikini "as is" and to the ethanol and acetone extracts. Patch testing with TLC strips showed a strong reaction to spots-fractions 3 and 4. GC-MS was performed to identify substances in each fraction and those suspected to be skin sensitisers were patch tested. On day (D) 4 positive reactions to ethylene glycol monododecyl ether (irritant reaction) and 2,4-dichlorophenol (++) were observed. CONCLUSION: A myriad of chemical compounds can be found in clothing. Ethylene glycol monododecyl ether and 2,4-dichlorophenol were identified as the potential culprits of this bikini TCD.

Contact allergy to polyhexamethylene biguanide (polyaminopropyl biguanide).

BACKGROUND: Polyaminopropyl biguanide (INCI name) and polyhexamethylene biguanide (PHMB) are polymeric biguanides. PHMB is a broad-spectrum antimicrobial substance used as a preservative in many products. Due to our limited knowledge on PHMB contact allergy frequency and the fact that cases of allergic contact dermatitis to PHMB might be missed, we have included PHMB as a screening allergen since 2016. OBJECTIVE: To report the prevalence of positive patch test reactions to PHMB as a screening allergen in patients with suspected allergic contact dermatitis. METHODS: A retrospective analysis of 1760 patch tested patients from July 2016 to December 2018 was performed. Polyaminopropyl biguanide 2.0% aqua was included in the extended Malmö baseline series during the study period. RESULTS: Of all patients, 1204 (68.4%) were female. Positive patch test reactions were reported in 19 patients (1.1%). The most common sites of lesions were face, head, and neck (52.6%). There was a significant correlation between concomitant reactions to PHMB and other cosmetic-related allergens. CONCLUSION: The prevalence of positive reactions to PHMB was higher than that previously reported. Patch testing with PHMB should be performed in patients with dermatitis who have lesions on the face, head, and neck.