Surveillance of occupational skin disease using the Supplementary Data System

The utility of the Supplementary Data System (SDS) compiled by the Bureau of Labor Statistics (BLS) in conducting surveillance of occupational skin disease was evaluated by examining 14,703 workers' compensation cases reported to the SDS for the year 1981. Combined with state employment denominators obtained from the BLS Employment and Earnings Program, rates of illness (cases of dermatitis/10,000 employed) calculated for eight major industrial divisions varied significantly according to the criteria used for reporting cases. Despite quantitative variations in the rate of skin disease that depended on specific reporting criteria, the relative ranking of the major industrial divisions remained unchanged, with highest rates of skin disease consistently found in three major industry divisions: agriculture, manufacturing, and construction. This ranking of major industry divisions by rate of dermatitis corresponded extremely well with rankings generated from the 1981 Annual Survey (Spearman rank correlation = .98, p less than .01). At the two-digit level of the Standard Industrial Classification, the rankings based on the SDS had a 77% rank correlation with those from the Annual Survey. Two-digit SIC codes identified from the top 10 in both sets of rankings included crop and livestock production from the agricultural division and leather products, food products, rubber and plastic products from the manufacturing division.

Patch testing discordance alert: false-negative findings with rubber additives and fragrances

From July 1996 through June 1998, the North American Contact Dermatitis Group evaluated 318 patients for suspected contact dermatitis by patch testing simultaneously with Finn Chambers and the T.R.U.E. Test allergen system. Discrepancies between the two systems were found in some of the results, particularly with fragrance and rubber allergens. These results suggest that positive reactions to fragrance, thiuram, and carba mix allergens may be missed if the T.R.U.E. Test is used alone.

A preliminary report of the occupation of patients evaluated in patch test clinics

BACKGROUND

The interplay between the occupational environment and worker's skin can result in contact dermatitis of both irritant and allergic types. Other forms of dermatitis can also be influenced by occupational exposures.

OBJECTIVE

The aim of this study is to compare the occupations and allergens of occupational contact dermatitis cases with nonoccupational contact dermatitis cases.

METHODS

Diagnostic patch testing with allergens of the North American Contact Dermatitis Group and occupational coding by the National Institute for Occupational Safety and Health methods.

RESULTS

Of 2,889 patients referred for evaluation of contact dermatitis, 839 patients (29%) were found to have occupational contact dermatitis. Of the 839 cases deemed occupational, 455 cases (54%) were primarily allergic in nature and 270 cases (32%) were primarily irritant in nature. The remaining 14% were diagnoses other than contact dermatitis, aggravated by work. The occupation most commonly found to have allergic contact dermatitis was nursing. Allergens strongly associated with occupational exposure were thiuram, carbamates, epoxy, and ethylenediamine.

CONCLUSION

Some contact allergens are more commonly associated with occupational contact dermatitis. Nursing and nursing support are occupations most likely to be overrepresented in contact dermatitis clinics.

Gold allergy in North America

OBJECTIVE

To determine the prevalence of allergic reactions to gold among patients tested by the North American Contact Dermatitis Group (NACDG) from 1996 to 1998.

METHODS

This is a prospective analysis of patch test results from the 12 centers that comprise the NACDG. Gold was tested as gold sodium thiosulfate (0.5% in petrolatum [pet]), along with 49 other screening allergens, in patients presenting with possible contact dermatitis.

RESULTS

Of 4,101 patients tested, 388 (9.5%) had a positive patch test result to gold. Women accounted for 62.8% of the subjects tested and 90.2% of patients positive to gold (P < .0001). The most common sites of dermatitis in gold-allergic patients were the hands (29.6%), face (19.3%), and eyelids (7.5%). Nickel and cobalt allergies, respectively, also were present in 33.5% and 18.3% of gold allergic individuals, as compared with 14.2% and 9.0% of the total population. Gold was the only positive reaction in 15.2% of the 388 patients.

CONCLUSION

Gold is a more common allergen than previously reported and might cause facial and eyelid dermatitis. Hypersensitivity to gold is statistically linked to female gender and to allergic reactions to nickel and cobalt.

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.

Allergic contact dermatitis from a lawn care fungicide containing dyrene

Lawn care chemicals are frequently blamed when skin rashes occur in lawn care workers, although proof of a cause-and-effect relationship is often lacking. A lawn care worker developed severe dermatitis of the hands, arms, face, and neck shortly after his company started using a new fungicide. Patch-testing proved that the dermatitis was caused by a contact allergy to Dyrene, the active fungicidal chemical.

The prevalence of back pain, hand discomfort, and dermatitis in the US working population

OBJECTIVES

The purpose of the study was to provide the health care and public health communities with national prevalence estimates of selected conditions in the US working population.

METHODS

National prevalence estimates of self-reported conditions among working people were calculated from data collected for the 1988 Occupational Health Supplement to the National Health Interview Survey.

RESULTS

The highest prevalence estimates were found among occupational groups. For example, the prevalence of back pain due to an injury at work among truck drivers was 6.7%; back pain due to repeated activities at work among mechanics and repairers of heavy equipment and machinery was 10.5%; hand discomfort among operators of machines that process metal, plastic, stone, and glass was 23.5%; and dermatitis due to contact with substances at work among physicians, dentists, nurses, pharmacists, and dietitians was 5.6%.

CONCLUSIONS

A substantial proportion of these conditions among occupational groups with the highest prevalence estimates are occupational in origin. These prevalence estimates identify occupations in which efforts are needed to prevent these conditions.

Dermatitis in workers exposed to antimony in a melting process

An employee at a brazing rod manufacturing plant developed a generalized eruption of follicular papules and pustules. His job tasks included breaking up antimony ingots and melting the pieces in a crucible; he was exposed to antimony metal dust and to antimony trioxide fumes. Two fellow employees who later performed the same job tasks developed similar eruptions. The clinical and workplace evaluations suggested that the fumes from melting antimony were the cause of the dermatoses, and that the current Occupational Safety and Health Administration permissible exposure limit is not adequate to prevent cutaneous effects of antimony exposure.

Prevention of occupational contact dermatitis

Contact dermatitis is the most frequent type of occupational skin disease. Although prevention of contact dermatitis in the workplace should ideally be accomplished through total elimination of cutaneous exposure to hazardous substances, this is often not feasible. Therefore eight basic elements of a multidimensional approach to prevention have been identified. These elements include recognition of potential cutaneous irritants and allergens, engineering controls or chemical substitution to prevent skin exposure, personal protection with appropriate clothing or barrier creams, personal and environmental hygiene, regulation of potential allergens and irritants within the workplace, educational efforts to promote awareness of potential allergens and irritants, motivational techniques to promote safe work conditions and practices, and preemployment and periodic health screening. A comprehensive prevention program based on this multidimensional approach requires the cooperative efforts of employees, employers, engineers, chemists, industrial hygienists, safety and supervisory personnel, union representatives, governmental agencies, and occupational health practitioners.

Surveillance of occupational skin diseases: a method utilizing workers' compensation claims

In order to determine the feasibility of using workers' compensation claims (WCC) for surveillance of occupational skin diseases, we reviewed all WCC received in the state of Ohio from 1980 through 1984. A total of 4,214 WCC for occupational skin diseases were filed by 2,610 Ohio companies, of which 1,656 (63%) companies were classified in Standard Industrial Classification (SIC) categories with average annual WCC rates above the overall state average for skin diseases. During the five year study period, 102 companies filed six or more WCC, of which 85 (83.3%) companies were classified in SICs with above-average WCC rates. WCC from 65 (63.7%) of these 102 companies implicated either the same occupation or causal agent in 50% or more of WCC received from each respective company. Using SIC classifications with WCC rates above the state average and six or more filed WCC as measures of risk, there was good correlation between company risk ranking by SIC categorization and number of WCC filed. This study suggests that active intervention strategies to prevent occupational skin diseases can be based on primary identification of companies filing WCC, followed by secondary identification of high-risk occupations or causal agent exposures within these companies.

Chloracne associated with employment in the production of pentachlorophenol

To evaluate the association between exposure to pentachlorophenol (PCP) and the occurrence of chloracne, we studied the medical and personnel records for individuals employed in the manufacturing of PCP. Forty-seven cases of chloracne were identified among 648 workers (7.0%) assigned to PCP production at a single plant between 1953 and 1978. The annual incidence rate varied considerably, ranging from 0 (in 1953) to 1.46 (in 1978). No linear trend in the risk of chloracne was observed with the duration of employment in the pentachlorophenol department. Workers with a documented episode of direct skin contact with PCP had a significantly increased risk of chloracne compared with workers who did not have a documented episode of direct skin contact (cumulative incidence ratio = 4.6; 95% confidence interval 2.6-8.1). Our results confirm that chloracne is associated with exposure to PCP contaminated with hexachlorinated, heptachlorinated, and octachlorinated dibenzo-p-dioxins and dibenzofurans.

Contact dermatitis and workers' compensation: criteria for establishing occupational causation and aggravation

Contact dermatitis is the most common form of occupationally acquired skin disease. Eligibility for coverage under the workers' compensation laws of all states requires only reasonable probability that dermatitis directly resulted from, or was aggravated by, employment. The responsibility for this determination ultimately resides with the examining physician, who must critically evaluate the medical history and cutaneous findings. This article proposes seven objective criteria that may be used to assess the probability of a causal relationship with employment.

Occupational skin diseases, United States. Results from the Bureau of Labor Statistics Annual Survey of Occupational Injuries and Illnesses, 1973 through 1984

The overall incidence rates, numbers, and proportions of occupational skin diseases recorded in the Bureau of Labor Statistics Annual Survey of Occupational Injuries and Illnesses, from 1973 through 1984, were reviewed, and a detailed analysis of occupational skin diseases recorded in the 1984 Annual Survey was performed. Overall incidence rates and numbers of cases declined from 1973 through 1983, but increased slightly in 1984. The major industrial divisions of agriculture and manufacturing have consistently had the highest rates and numbers of cases, respectively; skin diseases have accounted for almost two thirds of all occupational illnesses within agriculture. In the 1984 Annual Survey, 11 industries were ranked in the "Top 15" for both incidence rates and numbers of cases, at the two-digit Standard Industrial Classification level. At the four-digit level for manufacturing, four industries were also ranked in the "Top 15" for both indexes. This analysis has identified industries toward which research efforts should be directed to characterize those occupational activities or exposures most responsible for these higher risks.

Occupational vitiligo due to unsuspected presence of phenolic antioxidant byproducts in commercial bulk rubber

We investigated the occurrence of cutaneous depigmentation (vitiligo) among employees of a company that manufactured hydraulic pumps. The interiors of these pumps were injection-molded with rubber. We identified a small but significant cluster of vitiligo cases among a group of employees who frequently handled the rubber used in this injection molding process. Although none of the additives specified in the rubber formulations was a phenolic or catecholic derivative, known to be potential causes of chemically induced vitiligo, gas chromatographic analysis identified a para-substituted phenol (2,4-di-tert-butylphenol, DTBP) in solid samples of the most frequently used rubber. Surface wipe analysis confirmed that workers could be exposed to DTBP from simple handling of the rubber. We subsequently established that the solid bulk rubber used as the base in these stock rubber formulations contained both DTBP and smaller quantities of p-tert-butylphenol. Both had formed as unsuspected byproducts during chemical synthesis of two antioxidants added to the solid bulk rubber by a major rubber supplier. We conclude that the unsuspected presence of potential chemical depigmenting agents in solid bulk rubber, from which industrial rubber products are formulated, may contribute to the occurrence of occupational vitiligo, and that a simple review of ingredients in rubber formulations is inadequate to detect their presence.

Dermatitis from plastic tote boxes impregnated with an antistatic agent

An outbreak of dermatitis occurred among employees of a microelectronics firm. In a cross-sectional epidemiologic investigation, we found that dermatitis of the hands or arms had occurred among 14 of 29 (48.3%) employees of the incoming inspection department where plastic tote boxes recently purchased from one manufacturer had been used, compared to only one case among 17 (5.9%) employees in another department which had not used these boxes. Affected workers could detect an oily film on the surfaces of these new boxes, but not on older ones. We identified the oily film to be a surface accumulation of bis-hydroxyethyl-tallow amine (BHETA), an antistatic agent with which the tote boxes had been impregnated. Subsequent toxicologic investigation established that BHETA could provoke both follicular and nonfollicular irritant dermatitis, and was also a potential skin sensitizer. Antistatic agents should be considered as potential causes of dermatitis among employees who handle electrical parts transported in plastic boxes, particularly when affected employees can detect an oily film on the box surfaces.

Distribution of lost-work-time claims for skin disease in California agriculture: 1978-1983

In order to identify California agricultural workers at high risk for occupational skin disease, we evaluated the distribution of 2,722 claims for lost-work-time skin conditions reported between 1978 and 1983 by Standard Industrial Classification (SIC) and source of illness. In the overall work force, cases were most frequently attributed to plants (52.1%), chemical exposures (20.4%), and food products (12.5%), but considerable variation occurred in the distribution of cases among the subdivisions of agriculture. The forestry subdivisions (SICs 081, 082, 084, and 085) had the highest rate (given as cases/10,000 employed) of claims for skin disease attributed to plants (53.5), but no cases due to other exposures. For chemical exposures, the highest rate of claims occurred in the horticultural specialities (SIC 018) subdivision (5.1), but this group also had a significant claims rate for plant-related skin disease (15.9). The highest claims rate for cases attributed to food products occurred in the vegetables/melons subdivision (4.7), but this group had claims rates for exposure to plants (3.8) and chemicals (2.8) that were nearly as high. Efforts to evaluate and prevent skin disease in agricultural workers should recognize the complex range of exposures to which this work force is subject.

Post-traumatic eczema

Thirteen cases of eczema that followed acute cutaneous trauma were observed. On the basis of the present case series, the following conclusions may be drawn: 1. Cutaneous trauma may precipitate eczema. 2. The trauma is sufficient to cause obvious tissue damage accompanied by an inflammatory or regenerative response. 3. Eczema usually begins within a few weeks of acute injury at the site of the cutaneous trauma. 4. Eczema may occur as an isolated idiopathic reaction or as an isomorphic reaction either preceding or following the appearance of an endogenous eczematous condition in nontraumatized skin. 5. Individual lesions of post-traumatic eczema may persist or recur for long periods of time. 6. The occurrence of post-traumatic eczema following occupational injury has important medicolegal implications.

Allergic contact dermatitis from a nonbisphenol A epoxy in a graphite fiber reinforced epoxy laminate

An employee of the Composites Division of an aircraft engine manufacturing firm developed dermatitis associated with the handling of a graphite fiber reinforced epoxy laminate (epoxy prepreg). Patch test investigation demonstrated that the responsible causal agent was the nonbisphenol A epoxy binder, 4-glycidyloxy-N, N-diglycidylaniline. A patch test with bisphenol A epoxy from a standard patch test screening series was negative. Subsequent interviews with employees of the Composites Division suggested that a relative lack of awareness of the cutaneous hazards of fiber reinforced epoxy laminates, compared with liquid epoxy resin systems, may be an important risk factor for allergic sensitization to these composite materials.

Knuckle pads in live-chicken hangers

A study of live-chicken hangers in a poultry processing plant demonstrated a high prevalence of callosities over the knuckles (knuckle pads) of both hands. Knuckle pads were observed in 56% (23/41) of live-chicken hangers, but in no (0/41) workers from other departments (p less than 0.001). The probable cause was the repeated striking and sliding of the knuckles against metal shackles in which live birds were being placed. Additional medical and ergonomic evaluation would be worthwhile to confirm the probable cause, to determine whether associated tissue disorders are present in the digits of chicken hangers who develop knuckle pads, and to suggest preventive measures.

Surveillance of work-related cold injuries using workers' compensation claims

The usefulness of workers' compensation claims for the surveillance of occupational injuries was evaluated by analyzing claims for cold injury. Five hundred ten claims filed in 1983 from 23 states participating in the Bureau of Labor Statistics Supplementary Data System and an additional 147 claims filed with the Division of Safety and Hygiene of the Industrial Commission of Ohio from Jan 1, 1984, to June 30, 1985, were examined. As expected, the number of injuries per winter day increased as temperature decreased and wind speed increased. The rate of injury began to increase when temperatures fell below 10 degrees F and wind speeds exceeded 10 mph. These weather conditions were milder than previously published cold hazard charts suggest. Frostbite injuries of the lower extremities occurred at milder temperatures, required more lost workdays, and were more costly than cold injuries to the head and face or to the upper extremities. Industries with the highest rates of injury included agriculture, oil and gas extraction, trucking and warehousing, protective services, and interurban transportation. Injuries during nonwinter months involved the processing, distribution, and preparation of food. Vehicle breakdown or contact with water, gasoline, alcohol, or cold water were noted as contributing factors on many of the compensation claims. This probe suggests that claims for workers' compensation adequately reflect the expected association of environmental factors and the occurrence of cold injury.

Granulomatous reaction to purple tattoo pigment

An acute dermatitis overlying an immunologic granuloma was noted at the site of purple "dye" injection in a man with multiple multicolored tattoos. The skin reaction was observed 3 weeks after the injection, which proved to contain manganese, the usual metallic salt used for purple colored tattoos. Atomic absorption spectrometry showed a large amount of manganese in the biopsy specimen. Neither the dermatitis nor an immunologic granuloma could be reproduced with manganese salts or the alleged tattoo pigment. In addition, his peripheral blood lymphocytes were shown to be normal both in subset distribution and in their function, but these cells did not respond by blastogenesis to dilutions of the alleged pigment or to 2 manganese salts tested.

Contact dermatitis from use or misuse of soaps, detergents, and cleansers in the workplace

Personal hygiene is considered traditionally important in the prevention of occupational skin disease. Contact dermatitis may result not only from the correct use of soaps and detergents, leading to excessive or inappropriate exposure, but also from incorrect or inappropriate use of these products.

Delayed hypersensitivity to a corticosteroid suspension containing methylprednisolone. Two cases of conjunctival inflammation after retrobulbar injection

Two patients with chronic iridocyclitis had a delayed hypersensitivity reaction, characterized by severe conjunctival inflammation, after retrobulbar injections with a commercial suspension of methylprednisolone acetate. Although patch test reactions to methylprednisolone at enhanced concentrations were negative, delayed hypersensitivity could be easily demonstrated by intradermal testing with this corticosteroid. Both patients also had concomitant delayed hypersensitivity to a proprietary preservative (myristyl gamma-picolinium chloride) in the commercial corticosteroid suspension, which was confirmed by intradermal testing. These observations (negative patch test reactions, positive intradermal test reactions) suggest that the route of administration may be an important determinant of antigenic hapten-protein complex formation and subsequent delayed hypersensitivity responses involving cutaneous or mucocutaneous tissue.

The contact urticaria syndrome

Contact urticaria may occur following contact of the skin or mucous membranes with a large number of diverse substances. When localized angioedematous reactions of the eyes or oropharynx are caused by proteinaceous substances, the distinction between contact urticaria and common inhalant or food allergies is subtle. The time course of the reaction, negative controls, or occurrence of generalized symptoms do not constitute unequivocal evidence of immunologic contact urticaria, and confirmation by RAST or passive transfer testing is required. Clinical symptoms range from mild, localized erythema to generalized anaphylaxis. When contact urticaria becomes superimposed on eczematous skin, immediate reactions that resemble eczema more than urticaria may occur. Dermatologists must increase their awareness of these clinical reactions and evaluate the external environment when searching for causes of localized urticarial reactions.

Allergic contact dermatitis from anaerobic acrylic sealants

Three patients employed in electronic assembly operations had allergic contact dermatitis to polyethylene glycol (PEG) dimethacrylate, found in an anaerobic sealant. Clinical features in all three cases consisted of eczema localized predominantly on the distal parts of the fingers and the palmar aspects of fingertips; onycholysis developed in one patient. No cross reactions to methyl methacrylate were observed on patch testing. Guinea pig maximization testing with both the commercially available sealant and the active resin demonstrated that PEG dimethacrylate is a moderate skin sensitizer.

Allergic contact dermatitis from rosin used as soldering flux

Two cases of allergic contact dermatitis from soldering fluxes are reported. Both were caused by rosin (colophony). One case was confirmed by a positive patch test to rosin purchased from a commercial European patch test supplier. The other could be confirmed only by a positive patch test to the specific rosin used to flux the solder; repeated patch tests to rosin purchased from the same European supplier were negative. Dermatitis from soldering fluxes is reviewed.

Allergic contact dermatitis from 2-n-octyl-4-isothiazolin-3-one, a paint mildewcide

Severe allergic contact dermatitis from a paint mildewcide, 2-n-octyl-4-isothiazolin-3-one, developed in a worker formulating latex paints within a paint manufacturing company, Guinea pig maximization testing demonstrated this to be a moderate sensitizer. Further cases of allergic contact dermatitis may be encountered as the use of this biocide increases in the market place.

Contact urticaria from peanut butter

A patient with multiple atopic allergies, atopic facial dermatitis, and a generalized atopic skin diathesis developed (i) angioedema of the lips and tongue following ingestion of peanut butter, and (ii) localized urticarial reactions following direct skin contact. Open testing with peanut butter demonstrated probable immunologic contact urticaria. The relationship of contact urticaria to the atopic skin diathesis is discussed.

Perspectives in occupational dermatology

Because large surface areas of the skin are exposed directly to the environment, skin is an organ particularly vulnerable to occupationally induced disease. Statistics show that, excluding accidental injury, nearly half of all occupational illnesses occur in this organ; a fourth of all workers suffering from occupational skin disease lose an average of 10 to 12 workdays. The constant evolution of new industrial chemicals and methods of manufacture continue to bring new skin hazards and disease into the workplace. Occupational health physicians and practitioners, who usually have minimal training in dermatology, must diagnose and treat unfamiliar diseases in a setting of even less familiar, often overwhelming, technology. A thorough understanding of cutaneous defense mechanisms, clinical patterns of occupational skin disease and methods for establishing accurate diagnoses is essential.

Contact dermatitis from cyanide plating solutions

Two cases of contact dermatitis from electroplating solutions were attributed to irritation from cyanide salts. Both demonstrated similar clinical features. In neither could concomitant contact allergy to other constituents of the plating solutions be demonstrated. In one case, irritation could not be attributed to the alkalinity of the plating solution. Contact dermatitis from cyanide plating solutions may be associated with systemic symptoms, since cyanide is rapidly absorbed through the skin. Poor handling and hygiene techniques in the workplace should be corrected immediately.

Transepidermal water loss as a function of skin surface temperature

Transepidermal water loss (TEWL) was measured as a function of skin temperature, using human cadaver skin in modified skin diffusion chambers. A formula was derived to allow conversion of TEWL at any skin temperature to a standard reference temperature. This formula permits more accurate comparison of TEWL within and between subjects.