Human and economic impact of allergic contact dermatitis and the role of patch testing

Patch Testing Pearls

Dermatitis is one of the most common illnesses encountered by healthcare providers and the causes are numerous. Contact dermatitis is the form of dermatitis resulting from contact with the environment, and it may be either irritant or allergic in nature. Patch testing has been the gold standard for diagnosis of allergic contact dermatitis since its formal description over 100 years ago by Jadassohn. While this diagnostic tool may seem simple to us today, there are numerous potential points for error that the practitioner must keep in mind. Patient selection, technique of patch test placement, allergen selection, patch test reading and interpretation, and patient management all must be considered. To simply apply a given set of test allergens indiscriminately and not be prepared to interpret the results accurately with patient education and management in mind would be a great failure. Conversely, with experience and the proper knowledge base some of the most complex dermatitis questions can be answered.

The perceived obstacles in performing patch test to detect allergic contact dermatitis: a comparison between community allergists and directors of allergy training programs

BACKGROUND

Patch testing (PT) is the gold standard test to detect allergic contact dermatitis. Despite its usefulness, it is not universally performed in allergy practices.

OBJECTIVES

To determine obstacles in performing PT and to evaluate the differences in perception of these obstacles between community allergists and directors of training programs.

METHODS

Two anonymous Web-based questionnaires were distributed to 65 program directors (PDs) across the United States and to 200 community allergists in the mid-Atlantic region. Program directors and community allergists were categorized based on PT performance. Community allergists were categorized based on type of practice. Comparisons between categories were made using the chi2 test.

RESULTS

Perceived obstacles among community allergists and PDs were similar; this remained unchanged regardless of performing PT. When community allergists in solo practice were compared with those in group private practice, the difference in perception was significant (P < .01). Previous training in PT among PDs and community allergists was associated with a higher likelihood of performing PT.

CONCLUSIONS

Previous training in PT among PDs and community allergists was associated with a higher likelihood of performing PT. We recommend that training in the application and interpretation of PT for diagnosis of allergic contact dermatitis should be an integral part of the curriculum of allergy fellowship training programs and should also be incorporated into the continuing medical education program of practicing allergists. Furthermore, although allergists may continue to rely on dermatologists for more comprehensive PT, use of the thin-layer rapid use epicutaneous test is a simple screening tool that should be available to all allergy practices.

Dermatologist and family practitioner practice patterns for occupational contact dermatitis

Medical practitioners have a role in the recognition of occupational contact dermatitis. The longer the duration of symptoms before diagnosis, the poorer the outcome. Our objective was to understand practice patterns, barriers and needs for early diagnosis of occupational contact dermatitis. A survey to obtain information on practice patterns was developed based on the literature and interviews with dermatologists and family practitioners. The survey was sent to all dermatologists and a random sample of 600 family practitioners in Ontario. Fifty-seven per cent of dermatologists and 9% of family practitioners report seeing more than 20 patients per year with occupational contact dermatitis. The majority of practitioners report taking a workplace exposure history. Barriers to taking a workplace exposure history include time constraints and lack of knowledge. Reasons for referral to specialists include a lack of expertise, testing facilities and knowledge about workers' compensation, time constraints and inadequate reimbursement, whereas lack of access to specialists is a barrier for referral. Although most practitioners identify a need for further education, a low volume of patients and time constraints are key barriers to continuing education. Opportunities are identified to improve educational initiatives and health services delivery for occupational contact dermatitis, tailored to each practitioner group.

Structure?activity relationships for skin sensitization: recent improvements to Derek for Windows

Derek for Windows (DfW) is a knowledge-based expert system that predicts the toxicity of a chemical from its structure. Its predictions are based in part on alerts that describe structural features or toxicophores associated with toxicity. Recently, improvements have been made to skin sensitization alerts within the DfW knowledge base in collaboration with Unilever. These include modifications to the alerts describing the skin sensitization potential of aldehydes, 1,2-diketones, and isothiazolinones and consist of enhancements to the toxicophore definition, the mechanistic classification, and the extent of supporting evidence provided. The outcomes from this collaboration demonstrate the importance of updating and refining computer models for the prediction of skin sensitization as new information from experimental and theoretical studies becomes available.

Topical pimecrolimus in the treatment of human allergic contact dermatitis

BACKGROUND

Contact dermatitis is a common clinical problem, with prevalent sensitizers being cosmetics, metals, medicines, and plants. Plants of the Toxicodendron species cause allergic contact dermatitis (ACD) in 50% to 70% of the population. Pimecrolimus is an ascomycin macrolactam developed for the treatment of inflammatory skin diseases and approved by the US Food and Drug Administration for atopic dermatitis. There are studies supporting the effectiveness of macrolactams when administered before antigen challenge, but there are no studies describing the effectiveness of these drugs in the treatment of established human ACD.

OBJECTIVE

To investigate the effect of topical pimecrolimus in the treatment of Toxicodendron-induced ACD once rash is evident.

METHODS

Poison ivy tincture was applied to the bilateral anterior forearms of 12 subjects with Finn Chambers (Allerderm Diagnostic Products, Petaluma, CA). After dermatitis was evident, volunteers treated each arm twice daily with either 1% topical pimecrolimus cream or placebo in a blinded fashion. Outcomes measured were a dermatitis grading score and time to rash and itch resolution.

RESULTS

The median +/- SEM time for rash resolution was 16.55 +/- 1.59 days in the treatment group and 16.27 +/- 1.82 days in the placebo group (P = 0.601). The median time for itch resolution was 4.73 +/- 1.56 days in the treatment group and 4.91 +/- 1.59 days in the placebo group (P = 0.167). The average dermatitis score was 2.26 +/- 0.17 in the treatment group and 2.32 +/- 0.15 in the placebo group (P = 0.62).

CONCLUSIONS

The application of topical pimecrolimus is ineffective in the treatment of ongoing Toxicodendron-induced ACD.

An audit of the value of patch testing and its effect on quality of life

We have assessed the value of patch testing from the patient's perspective and examined the impact of patch testing on their quality of life (QoL). 140 patients were recruited over 5 months. 2 questionnaires were designed to investigate the patient's views on patch testing. The 1st questionnaire was completed at the final visit to the clinic and the 2nd was posted 6 weeks later. The Dermatology Life Quality Index (DLQI) questionnaire was completed on both occasions. There was a significant improvement of the DLQI score in all patch-tested subjects (P = 0.003). Patients with involvement of the trunk had worse QoL. At the 4-day visit, 77 patients (55%) expressed the opinion that patch testing had been helpful. 6 weeks later, 71 patients replied. 47 patients were diagnosed as having allergic contact dermatitis: 87% of them found that patch testing had been useful, 91% were able to avoid the allergen(s) and 57% reported improvement/clearing in their skin condition. 58% of the 24 patients with negative results also found that patch testing had been beneficial. Overall, patient perception was that they understood verbal information (92%) better than written information (76%). Patch testing is beneficial to patients, leading to improved QoL. Patient perception was that they understood verbal advice better than written information.

Langerhans cells that express matrix metalloproteinase 9 increase in human dermis during sensitization to diphenylcyclopropenone in patients with alopecia areata

BACKGROUND

We know little of the initial events during the sensitization phase of contact allergy in humans. Alopecia areata (AA), a disease of unknown pathogenesis characterized by patchy hair loss, may be treated by inducing contact allergy to diphenylcyclopropenone (DPC), later followed by its topical application.

OBJECTIVES

To learn more about the initial events during sensitization in human skin, we studied the early events during induction of contact allergy to DPC in patients with AA.

METHODS

DPC 2% and sodium lauryl sulphate (SLS) 4% were applied on the backs of eight patients with AA. Punch biopsies were taken 6 and 24 h after application. The biopsies were snap-frozen and cryostat sections were evaluated with immunohistochemistry using antibodies against CD1a, HLA-DR, CD3, CD54 and matrix metalloproteinase 9 (MMP-9).

RESULTS

After 24 h all subjects exhibited erythema on the DPC-treated areas. Histological evaluation of biopsies from these areas showed hydropic degeneration and a significantly increased number of MMP-9+ cells in the dermis (P < 0.0005). The MMP-9+ cells were identified with double immunofluorescence staining as CD1a + Langerhans cells. The expression of the other markers studied remained unaltered irrespective of treatment, including treatment with SLS.

CONCLUSIONS

Our findings show that DPC induces an irritant reaction leading to an increased number of MMP-9+ CD1a+ cells in the dermis during the initial phase of sensitization.

The importance of a dedicated patch test clinic

BACKGROUND

A specialist patch test clinic was set up in April 1997 at the Department of Dermatology, South Infirmary-Victoria Hospital, Cork, Ireland. The number of batteries available was expanded from six to 21 and the routine testing of patients to their own products was introduced, as was prick testing for latex hypersensitivity.

OBJECTIVES

To assess the impact of introducing this clinic on the detection of allergic contact dermatitis.

METHODS

Patch test results for the first full year of operation of the clinic (1998) were compared with those in the year prior to setting it up (1996).

RESULTS

Although the number of patients tested rose after the introduction of the new clinic, the difference was not significant as the number of new dermatology general referrals had also risen. Thirty-one of the 91 patients tested in 1996 had positive patch tests compared with 84 of 158 tested in 1998 (P = 0.0036). Eighteen allergens were detected in 1996 and 53 in 1998. Two patients were positive to their own products in 1996, compared with 12 in 1998 (P = 0.04). The commercial batteries were negative in four of these cases. Three cases of latex hypersensitivity were detected in 1998.

CONCLUSIONS

The introduction of a specialist patch test clinic resulted in an increase in detected cases of allergic contact dermatitis. The larger range of batteries available and the more widespread testing of patients' own products were the principal factors involved.

An audit to identify the optimum referral rate to a contact dermatitis investigation unit

The principle of patch testing is to identify individuals with a contact allergy of relevance to their disorder and to provide avoidance advice in an attempt to improve or resolve their condition. We aimed to define an optimum referral rate to a centralized contact dermatitis unit using a retrospective analysis of data relating to 10 consultants. The results showed no significant difference (P = 0.21) in the percentage of relevant positive individuals identified between the consultants. However, a linear relationship (r = 0.99) was seen between the number of relevant positive allergic reactions and the number referred by individual consultants. We propose that the minimal annual referral rate for patch testing from a predominately urban population in a developed country is one in 700 of the population.

North American Contact Dermatitis Group patch test results for the detection of delayed-type hypersensitivity to topical allergens

BACKGROUND

Allergic contact dermatitis is a significant cause of cutaneous disease affecting many individuals. Patch testing, when used properly, often provides support for the diagnosis of allergic contact dermatitis.

OBJECTIVE

This article reports patch testing results from July 1, 1994, to June 30, 1996, by the North American Contact Dermatitis Group (NACDG).

METHODS

Patients evaluated in our patch test clinics were tested with the same screening series of allergens by the use of a standardized patch testing technique. The data from these patients were recorded on a standard computer entry form and analyzed.

RESULTS

Forty-nine allergens were tested on 3120 patients. Budesonide was added to the series in July 1995 and tested on 1678 patients. Of these patients, 66.5% had positive allergic patch test reactions, and 57% had at least one allergic reaction that was felt to be clinically relevant to the present or past dermatitis. The 20 screening allergens commercially available to United States dermatologists in the Allergen Patch Test Kit, accounted for only 54.1% of the patients with positive allergic reactions. The additional 30 allergens on the NACDG screening series accounted for 47% of patients with positive allergic reactions. Had the Allergen Patch Test Kit alone been used, 12.4% of all patients tested may have had their disease misclassified as a nonallergic disorder, and an additional 34.4% of all tested patients would not have had their allergies fully defined. Among those patients with positive responses to the supplemental allergens, 81% of the responses were of present or past relevance. The 12 most frequent contact allergens were nickel sulfate, fragrance mix, thimerosal, quaternium-15, neomycin sulfate, formaldehyde, bacitracin, thiuram mix, balsam of Peru, cobalt chloride, para-phenylenediamine, and carba mix. The present relevance varied with the specific allergen from 10.7% (thimerosal) to 85.7% (quaternium-15). Among newer allergens, methyldibromoglutaronitrile/phenoxyethanol (cosmetic preservative) caused positive allergic reactions in 2% of the patients; tixocortol-21-pivalate and budesonide (corticosteroids), in 2.0% and 1.1% of the patients, respectively; and ethylene urea/melamine formaldehyde mix (textile resin), in 5% of the patients.

CONCLUSION

The usefulness of patch testing is enhanced with the number of allergens tested, because allergens not found on the commercially available screening series in the United States frequently give relevant allergic reactions.