A patch testing and cross‐sensitivity study of carbamazepine‐induced severe cutaneous adverse drug reactions

Background The usefulness of the drug patch testing for Stevens–Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) is still controversial. Recent studies have shown that HLA‐B*1502 is strongly associated with CBZ‐SJS/TEN in Chinese and Southeast Asian populations. Objective To evaluate the usefulness of patch tests for patients with carbamazepine (CBZ)‐induced SJS, TEN and drug reaction with eosinophilia and systemic symptoms (DRESS) and the cross‐reactivity in patch tests among the aromatic antiepileptic drugs. Methods We measure the frequency of positive patch test reactions and cross‐sensitivity to structure‐related aromatic anti‐epileptic drugs (AEDs) for patients after SJS/TEN or DRESS episodes caused by CBZ. CBZ and other structure‐related AEDs used for patch testing were prepared in 10% and 30% petrolatum. Secondary measures included the association of HLA‐B*1502 genotype and frequency of possible side effects from the patch tests. Results Positive patch test reactions to 30% CBZ in the CBZ‐SJS/TEN were 62.5% (10/16), and 70% (7/10) in the CBZ‐DRESS. None of the 10 healthy controls displayed a positive reaction to tested agents. Cross‐sensitivity to other aromatic AEDs was observed in both the CBZ‐SJS/TEN and the CBZ‐DRESS. Only the HLA‐B*1502 genotype was present and strongly associated with the CBZ‐SJS/TEN, but not with the CBZ‐DRESS. Conclusion Drug patch testing is a safe and useful method for the identification of CBZ as the culprit drug of SJS/TEN as well as DRESS. Testing of chemically or pharmacologically related AEDs may provide information on cross‐reactivity for these patients.     

Delayed hypersensitivity to topical corticosteroids

Topical hypersensitivity to corticosteroids was studied by epicutaneous testing using the Finn Chamber technic. The steroids were tested in both ethanol and white petrolatum and, in certain cases, in dimethyl sulfoxide. Additionally, commercial preparations were tested. Three groups of patients were studied: (1) patients with a history of hypersensitivity to at least two topical preparations (five of ten patients studied showed a positive patch test reaction for corticosteroids), (2) patients in whom topical corticosteroid hypersensitivity was suspected because of treatment-resistant eczema (seven of twenty-five patients showed a positive patch test reaction), and (3) dermatologic inpatients and outpatients undergoing epicutaneous testing for suspected topical hypersensitivity. Hydrocortisone-17-butyrate (H-17-B) was included in the standard patch test series; of 450 patients tested, two showed a positive patch test reaction. All the patients with corticosteroid hypersensitivity had a positive reaction to H-17-B. In six patients, additional hypersensitivities to one or several other steroid preparations were seen. Use testing was performed as an open test, with 0.1% or 1% H-17-B in ethanol on normal skin of the flexor side of the upper extremities. A positive test reaction was seen in only one of nine patients. Results of use testing with the commercial 0.1% H-17-B (Locoid) ointment were always negative. Our study suggests that the sensitivity of patch tests for corticosteroid hypersensitivity can be increased by using ethanol as vehicle.     

Elicitation response characteristics to permanent hair dye in paraphenylenediamine-allergic volunteers

BACKGROUND: Elicitation response characteristics to complete permanent hair dye products in paraphenylenediamine (PPD)-allergic volunteers have not previously been explored in detail. OBJECTIVES: To assess the elicitation response characteristics observed in PPD-allergic volunteers upon patch testing with complete hair dyes. METHODS: PPD-allergic volunteers were assigned to 1 of 3 groups depending upon whether they elicited + (group 1), ++ (group 2) or +++ (group 3) reactions following the standard diagnostic procedure. Each group was subsequently patch tested with 2 complete hair dyes (A and B) for 30 min, 1 hr and 24 hr. Patch sites were examined 1 day, 2 days and 3 days after patch removal. RESULTS: Exposure to either hair dye for 30 min or 1 hr was insufficient to yield positive patch test reactions in all of the PPD-allergic patients in groups 1 or 2. Application of either hair dye for 24 hr was sufficient to yield positive reactions in all of the individuals within groups 2 and 3. CONCLUSIONS: The frequency of positive patch test reactions observed following 24-hr exposure to complete permanent hair dyes is comparable to that observed following 48-hr exposure to 1% PPD/petrolatum in those individuals whose degree of sensitization is such that they typically present ++ or +++ reactions diagnostically.     

Contact hypersensitivity reaction to ovalbumin in newborn guinea pigs from maternally sensitized animals.

An animal study was conducted to elucidate the role of ovalbumin (OA) in the development of eczematous lesions in intrauterine sensitized newborns. Four groups of pregnant guinea pigs were used: group A, immunized by oral administration of 1% OA in drinking water until parturition; group B, immunized by intradermal injection of OA with Freund's complete adjuvant; group C, immunized by both methods; and group D (control), not immunized. The newborn guinea pigs of each group were patch tested with 10% OA in white petrolatum. Positive reactions were seen in the newborns of groups B and C, but not in those in groups A and D. By enzyme-linked immunosorbent assay and passive cutaneous anaphylaxis, a high titre of OA-specific IgG was detected in the group B and C newborns. The number of positive patch test reactions decreased concomitantly with the decline of specific IgG. Histologically, eczematous changes were observed in the positive reaction sites. Many OA antigen-bearing Langerhans cells were found by the immuno-double labelling technique. Immuno-electron microscopic findings revealed the presence of OA antigens as well as IgG molecules on the cytoplasmic membranes of Langerhans cells. Our studies demonstrated that maternal sensitization with OA can induce an eczematous reaction in the newborns to OA patch testing under the presence of high levels of OA-specific IgG in the serum. From these findings it is suggested that IgG plays an essential role in the development of contact hypersensitivity reaction to OA.     

High frequency of false-positive reactions in attempted patch testing with acrylate/methacrylate mixes

Background. Although acrylate/methacrylate allergy has been frequently reported, until now patch testing with this group of allergens has been unwieldy, requiring the application of large supplementary series in most centres. Objectives. To formulate and evaluate two mixes of acrylate/methacrylate allergens in three centres (Malmö, Singapore, and Leuven). Patients/materials/methods. All patients tested with the baseline series during the study period were also patch tested with the mixes. Mix 1 consisted of: triethyleneglycol diacrylate (TREGDA) 0.1% wt/wt, 2‐hydroxyethyl methacrylate (2‐HEMA) 1.0% wt/wt and ethyleneglycol dimethacrylate 1.0% wt/wt in petrolatum. Mix 2 consisted of: TREGDA 0.1% wt/wt and 2‐HEMA 2.0% wt/wt in pet. The separate components of the two mixes were also tested simultaneously. Results. There were 25 (5 males; 20 females) positive reactions to mix 1 with 16 in Malmö, 8 in Singapore, and 1 in Leuven. Positive reactions to mix 2 were seen only in Malmö, in 8 female patients. Thus, the positive reaction rate for mix 1 was 8.3% overall (Malmö 7.7%, Singapore 18.6%, and Leuven 2.1%), and that for mix 2 was 2.7% overall (Malmö 3.8%, Singapore 0%, and Leuven 0%). Of the 16 positive reactions to mix 1 in Malmö, only 4 were considered to be true allergic reactions, as the component allergen testing gave totally negative results in 12/16. For mix 2, only 3/8 positive reactions were considered to be true allergic reactions, as the component testing was negative in 5/8. Many doubtful (10–20%) and positive but non‐allergic reactions were recorded, leading to early termination of the study. Conclusions. Although this was an unsuccessful attempt to formulate an acrylate/methacrylate mix, our experience will be useful for those embarking on future attempts to do this.     

P20 Red tattoo reactions

Tattoos are becoming increasingly popular, although reactions to tattoos remain relatively uncommon. We describe 4 patients with a variety of red tattoo reactions, one responding well to intralesional steroid therapy. Case 1: A 50‐year‐old man presented with a florid, inflammatory reaction confined to the red area of his forearm tattoo. Biopsy showed a dense lymphocytic and focal macrophage response to tattoo pigment. Mass spectrometry of biopsy tissue revealed high concentrations of titanium and iron. Patch testing was negative. Intralesional steroid injection has produced a marked improvement. Case 2: A 42‐year‐old man presented with an inflammatory reaction affecting the red area of his leg tattoo. Biopsy revealed a florid lymphoid reaction. Case 3: A 30‐year‐old man presented with an eczematous reaction within the red/brown pigmented areas of his tattoos, which was exacerbated by sun exposure. Patch testing showed a (+) positive reaction to cadmium after 96 hours. Photo patch testing was negative. The reaction settled spontaneously within 12 months. Case 4: A 37‐year‐old woman presented with a florid, indurated inflammatory reaction involving the red area of a shoulder tattoo. Patch testing revealed a (++) and (+) positive reaction to nickel and cobalt respectively with a doubtful (?+) reaction to mercury 0.5% in petrolatum after 96 hours. Tattoo reactions, especially red tattoo reactions can present with a spectrum of histological changes, including lichenoid, granulomatous, hypersensitivity, nodular, pseudolymphomatous or sarcoidal reactions. One of our cases responded well to intralesional steroid injection and one case resolved spontaneously.     

Citral a fragrance allergen and irritant

Citral is a well known contact allergen and a contact irritant. Routine patch testing in the past may have been restricted because of possible irritant (IR) patch test responses. 586 consecutive patients, with hand eczema, were patch tested with a selection of fragrances including citral 2% petrolatum and the European standard series. 28 of the patients showed a positive patch test reaction (+ to +++) to citral and 82 at least 1 IR patch test reaction and no positive patch test reaction to citral. A statistically significant association between a positive patch test reaction to citral and positive patch test reactions to other fragrances compared with IR reactions (n = 82) was established. The difference regarding fragrance history found between those with IR and positive reactions to citral was not significant. Citral could be an allergen and/or irritant, worthy of further more extensive studies.     

Petechial reaction following patch testing with cobalt

A total of 132 patch tested patients reacted with petechial reactions to cobalt chloride 1 % in petrolatum; 23 were retested with various concentrations of cobalt. In about 60% of those retested the petechial reaction could be reproduced. Histopathological examination showed slight perivascular tymphocytic infiltration, swollen endothelium and extravasation of erythrocytes but no signs of vasculitis.
It is suggested that in predisposed patients the petechial reaction following patch testing could be the result of primary irritation.     

Contact allergy to beryllium chloride: report of 12 cases

Background. Isolated cases of allergic contact dermatitis, gingivitis and stomatitis caused by beryllium have been previously reported. We have been able to study a series of 12 patients with patch test reactions to beryllium chloride. Objectives. The study was aimed at defining the clinical and patch testing characteristics in this group of patients, and determining whether some were delayed elicitation reactions or late reactions of active sensitizations by patch testing. Material and methods. We performed a 5‐year retrospective study of patients tested with a metal series, and studied a subgroup who showed reactions to beryllium chloride. Results. A total of 1799 patients were patch tested, 62 of whom were also tested with a specific metal series; 12 of them reacted to beryllium chloride. Eight of the 12 patients showed reactions to other metals. Based on the time of positive reaction to beryllium chloride, three patterns emerged: (i) 3 patients showed positive reactions on D2–D4; (ii) 6 patients showed positive reactions between D7 and D10; and (iii) 3 patients showed positive reactions later than D10. Conclusions. Contact allergy to beryllium chloride may not be as unusual as the literature suggests. In order to avoid undetected contact allergies, we recommend performing later readings, between D7 and D10, whenever patch testing is performed with beryllium chloride. Active sensitization may occur.     

Targeted testing with diethylthiourea often reveals clinically relevant allergic contact dermatitis caused by neoprene rubber

Background. Diethylthiourea is widely used in the rubber industry, particularly in neoprene rubber, and may cause allergic contact dermatitis. However, as thiourea allergens are not part of the European baseline series, the diagnosis of allergic contact dermatitis caused by thiourea compounds depends on clinical suspicion and aimed testing. Objectives. The aims of this study were to evaluate the occurrence of sensitization to diethylthiourea during a 19‐year period by using data from the Allergen Bank database at the Department of Dermatology and Allergy Centre, Odense University Hospital, and to evaluate whether the yield of aimed patch tests with diethylthiourea differed between the dermatologists in practice and those working in the dermatology department. Patients and methods. A total of 239 patients were patch tested with diethylthiourea 1% in petrolatum obtained from the Allergen Bank. The records for patients with positive reactions were evaluated retrospectively. Results. One hundred and fifty‐one patients were tested by 27 different dermatologists in private practice, and positive reactions were found in 16% (24/151) of the patients; 88 patients were tested at the dermatology department, and positive reactions were found in 15% (13/88). Thus, 15% (37/239) had positive patch test reactions to diethylthiourea, all with current clinical relevance and all strong. Conclusion. Clinical suspicion of neoprene rubber allergy and subsequent aimed patch testing with diethylthiourea give a high yield of clinically relevant allergic patch test reactions for both dermatologists in practice and dermatologists in the hospital department.     

Drug‐reaction eosinophilia and systemic symptoms and drug‐induced hypersensitivity syndrome

Drug reaction with eosinophilia and systemic symptoms (DRESS), also known as drug‐induced hypersensitivity syndrome (DIHS), is a rare, severe cutaneous adverse reaction characterised by fever, rash, lymphadenopathy, eosinophilia and/or other leukocyte abnormalities, and internal organ involvement and often has a relapsing–remitting course despite withdrawal of the drug. The drugs that are most implicated include aromatic anticonvulsants, allopurinol, sulphonamides, antiretrovirals (abacavir and nevirapine), and minocycline. The pathogenesis of DRESS/DIHS is far from clear but probably involves a combination of impaired pharmacokinetics and the accumulation of drug metabolites, the sequential reactivation of the herpesvirus family and genetic susceptibility conferred by the association with certain human leukocyte antigen (HLA) class I alleles. The strong association between abacavir and HLA‐B*5701 has enabled pharmacogenetics screening to be employed successfully to minimise the occurrence of hypersensitivity. A prolonged course of oral corticosteroids is required to treat DRESS/DIHS, given the relapsing–remitting nature of the condition with i.v. immunoglobulin and valgangciclovir reserved for refractory or life‐threatening cases.     

Skin reaction to dithranol and its modification by the addition of tar (LCD)

In spite of 70 years' continuous use of dithranol for the topical treatment of psoriasis, there are few reports of contact hypersensitivity reactions to this compound. A male patient with psoriasis had an adverse skin reaction to the traditional topical dithranol treatment; patch tests revealed contact dermatitis in response to 0.02% dithranol in petrolatum, which was characterized by marked erythema and severe bullous reaction to 0.1% dithranol in acetone. A control group of ten volunteers tested under similar conditions did not react with marked erythema until a concentration of 0.1% dithranol in petrolatum was applied. When liquid tar (5% liquor carbonis detergens, LCD) was added to the patch test solutions concentrations that were clearly one or two steps higher were needed before the erythematous skin reaction was induced. Since minimal erythema generally appears in patch tests with greater than or equal to 0.05% dithranol in petrolatum, we believe that in the patient reported here contact hypersensitivity to dithranol was present. The development of large perilesional erythematous areas with accompanying edema during topical dithranol treatment supports this suggestion. It seems that the addition of liquid tar elevates the reaction threshold to dithranol in hypersensitive patients with psoriasis.     

Delayed-type hypersensitivity to lidocaine

BACKGROUND: Lidocaine hydrochloride is the preferred anesthetic agent used in outpatient surgical procedures. While type I hypersensitivity reactions to lidocaine are uncommon, type IV hypersensitivity is reported even less frequently. OBSERVATIONS: Between January 1, 2001, and December 31, 2001, 183 patients were patch tested at the Penn State Milton S. Hershey Medical Center (Hershey, Pa) to the North American Contact Dermatitis Group tray. All patients who had a positive patch test reaction to lidocaine were challenged with 0.1 mL of preservative-free 1% lidocaine intradermally. Of the 183 patients patch tested, 4 had positive reactions to lidocaine, 2 of whom had histories of sensitivity to local injections of lidocaine manifested by dermatitis. CONCLUSIONS: Delayed-type hypersensitivity to lidocaine may occur more frequently than previously thought. In cases of suspected lidocaine contact type IV sensitivity, patients should be patch tested to lidocaine. Positive patch test reactions should be confirmed by intradermal challenge with lidocaine. To provide the patient with alternative local anesthetics, patch testing should be performed with other injectable anesthetics. If positive patch test results occur, intradermal testing should follow.     

Adverse drug reactions in dermatology

Adverse drug reactions (ADRs) – that is, unintended and harmful responses to medicines – are important to dermatologists because many present with cutaneous signs and because dermatological treatments can cause serious ADRs. The detection of ADRs to new drugs is often delayed because they have a long latency or are rare or unexpected. This means that ADRs to newer agents emerge only slowly after marketing. ADRs are part of the differential diagnosis of unusual rashes. A good drug history that includes details of drug dose, time‐course of the reaction and factors that may make the patient more susceptible, will help. For example, Stevens–Johnson syndrome with abacavir is much commoner in patients with HLA‐B*5701, and has a characteristic time course. Newer agents have brought newer reactions; for example, acneiform rashes associated with epidermal growth factor receptor inhibitors such as erlotinib. Older systemic agents used to treat skin disease, including corticosteroids and methotrexate, cause important ADRs. The adverse effects of newer biological agents used in dermatology are becoming clearer; for example, hypersensitivity reactions or loss of efficacy from antibody formation and progressive multifocal leucoencephalopathy due to reactivation of latent JC (John Cunningham) virus infections during efalizumab treatment. Unusual or serious harm from medicines, including ADRs, medication errors and overdose, should be reported. The UK Yellow Card scheme is online, and patients can report their own ADRs.     

Finding the optimal patch test material and test concentration to detect contact allergy to geraniol

Background. Geraniol is a commonly used fragrance terpene, and is tested in the baseline series in fragrance mix I. Geraniol is a pro‐hapten and a pre‐hapten, and sensitizers are formed in the autoxidation and skin metabolism of geraniol. Previous patch testing with air‐exposed (oxidized) geraniol has suggested that oxidized geraniol could be a better marker for contact allergy to geraniol than pure geraniol. Objectives. To find the optimal patch test substance and concentration for detecting contact allergy to geraniol. Patients and methods. Six hundred and fifty‐five patients were patch tested with pure and oxidized geraniol at 4.0%, 6.0% and 11.0% in petrolatum. Before patch testing, the irritant properties of pure and oxidized geraniol were studied in 27 patients at 2.5%, 5.0%, 10.0% and 20.0% pet. Results. Pure geraniol detected positive reactions in 0.15–1.1% of the patients, and oxidized geraniol detected positive reactions in 0.92–4.6% of the patients. Reactions to pure geraniol in patients not reacting to oxidized geraniol indicated metabolic activation of geraniol. Neither pure nor oxidized geraniol gave significant irritant reactions. Conclusions. Increasing the test concentrations of pure and oxidized geraniol enables the detection of more cases of contact allergy. Oxidized geraniol detects more patients than pure geraniol, but patch testing with only oxidized geraniol does not detect all cases of contact allergy to geraniol.     

Type IV hypersensitivity reactions to natural rubber latex: results of a multicentre study

BACKGROUND: Positive patch test reactions to natural rubber latex (NRL) have been interpreted as allergic or irritant by different groups. Additives to the NRL test solution have also caused positive reactions in previous studies. OBJECTIVES: Five centres of the British Contact Dermatitis Group conducted a prospective study on the prevalence of type IV hypersensitivity to NRL, using ammonia-preserved NRL solution for testing. PATIENTS AND METHODS: A total of 2738 consecutive patients were patch tested. Where clinically indicated, specific IgE was measured or a prick test done. RESULTS: Twenty-seven patients (1%) had a positive patch test reaction to NRL, which was considered to be allergic and of current relevance in 19 (70%) patients. Fourteen of these also had a positive prick test or specific IgE. Thirteen patients (48%) were male, 19 (70%) atopic and 13 (48%) had eczema on their hands. CONCLUSIONS: We conclude that delayed-type hypersensitivity to NRL is a problem for a proportion of patients with eczema, particularly on their hands, and that patch testing with ammonia-preserved NRL can be recommended to identify these patients. Patients with a positive patch test should be investigated for contact urticaria to NRL.     

White petrolatum (Ph. Eur.) is virtually non-sensitizing. Analysis of IVDK data on 80 000 patients tested between 1992 and 2004 and short discussion of identification and designation of allergens

Sporadic cases of contact allergy to white petrolatum, which is used as a vehicle in patch test preparations, have been reported. The quantitative relevance of the phenomenon remains yet to be elucidated. Methods: Retrospective analysis of patch test data of the Information Network of Departments of Dermatology (IVDK, http://www.ivdk.org) between 1992 and 2004. Results: Analysis of 79 365 patients patch tested with pure petrolatum yielded 27 '+' (0.03%) and 2 '+++' (0.003%) reactions. The majority of non-negative reactions (0.3%) was interpreted as doubtful (235) or mild irritant (32). The negative reaction index (RI) (-0.8), and the high positivity ratio (PR) (93%) especially a lack of concordance with patch test preparations containing > or=99% petrolatum indicate that many of the 'positive' (+) reactions have to be considered as irritant. There were 2 '+++' reactions. In 1 case, an 'angry back reaction' was confirmed. The other case is probably a reading or documentation error, as the majority of patch test reactions to preparations containing petrolatum remained negative in this case also. Conclusions: True allergic patch test reactions to white petrolatum are extremely rare and probably due to an individually increased susceptibility to allergens and/or irritants. This is in agreement with considering petrolatum as a non-sensitizer.     

Characteristics of patch test reactions to common preservatives incorporated in petrolatum and water, respectively

Background. The irritant properties of some preservatives and the use of water as the patch test vehicle for some of them call for a critical evaluation of patch test reactions to preservatives. Objectives. To examine the association between test vehicle (petrolatum versus water) or the patients' age and history of atopic dermatitis, respectively, and certain patterns of reaction to preservatives. Patients/methods. Data of 34 631 patients tested in 34 centres with 11 common preservatives were retrospectively analysed. The dynamic reaction patterns, reaction indices (RIs) and positivity ratios (PRs) were statistically evaluated. Results. All preservatives yielded more crescendo reactions in older than in younger patients. For 10 of 11 preservatives, the percentage of crescendo reactions was slightly higher in patients without a history of atopic dermatitis, and for 10 of 11 agents the RI was higher in patients with a positive history of atopic dermatitis. No consistent vehicle‐related effects on reaction characteristics were found. Chlorhexidine digluconate 0.5% in water and sodium benzoate 5% in petrolatum had the lowest RIs, highest PRs, and lowest proportions of crescendo reactions. Conclusions. Water as a vehicle is unlikely to affect the reaction patterns of preservatives. The generally used patch test preparations of chlorhexidine digluconate and sodium benzoate need improvement.     

P22Patch testing with p‐toluene diamine (PTD) preparations of different ages

Background: PTD, a component of oxidative hair dyes, is a frequent sensitizer in hairdressers. Investigations on the stability of the patch test preparation PTD 1% pet. revealed a decline of the PTD concentration to 0.1% within 6 months, possibly due to a reaction of PTD molecules to dye complexes. This raises the question if the long‐term diagnostic quality of the PTD preparation is hampered by chemical changes. Objective: To systematically compare intra‐individually patch test results obtained with three PTD patch test preparations of different age, tested synchronously in a multicenter study of the German Contact Dermatitis Research Group (DKG). Methods: 3 PTD preparations, produced in January 2002 (batch A), August 2001 (batch B), and April 2001 (batch C), were patch tested in 177 patients from March to December 2002. Patch testing was performed blinded, with respect to the production date. Results: There were 150 concordant reactions to batch A, B, and C, i.e. 133 negative, 1 doubtful (?), 11 weak positive (+), 3 strong positive (++ and +++), and 2 irritant reactions. In 27 patients, discordant reactions to batch A, B, and C had been observed. Altogether, 22 positive reactions were noted to batch A, and 19 to batch B and C, respectively (difference not significant). There was no clear cut time trend concerning the occurrence of positive or discordant reactions. Conclusions: Reproducibility of patch test reactions was within a normal range. The chemical changes mentioned above apparently do not affect the diagnostic quality of the PTD patch test preparation.     

Value of patch tests in clindamycin-related drug eruptions

Background. Patch tests help to confirm the aetiology of the cutaneous adverse drug reactions involving delayed hypersensitivity mechanisms, but the results vary with the pattern of skin reaction and the culprit drug. Objectives. To analyse the results of patch tests in patients with cutaneous adverse drug reactions imputable to clindamycin and assess their contribution to the diagnosis. Patients and methods. Between 2005 and 2009, we studied patients with delayed cutaneous adverse drug reactions following administration of clindamycin, usually associated with other drugs. After resolution of the cutaneous adverse drug reaction, patch tests were performed with a series of antibiotics, including pure clindamycin 10% in petrolatum. Results. We studied 30 patients (23 females and 7 males) aged 33–86 years (mean 59.97 years) with generalized maculopapular exanthema where clindamycin was among the highly suspected drugs. Two patients had a previous positive involuntary rechallenge. Patch tests with clindamycin were positive in 9 of 30 patients (30%). More than 50 control patients patch tested with clindamycin were negative. Discussion. We considered the positive patch tests results with clindamycin, in the 9 patients with maculopapular exantema, to be specific, versus the negative results observed in the control group. Although the sensitivity is low (30%), they confirmed the responsibility of this antibiotic in cutaneous adverse drug reactions in which, with only chronological criteria, it was not possible to conclude on the culprit drug.