Skin bioengineering in the noninvasive assessment of cutaneous aging

Cutaneous changes induced by aging can be quantified and monitored noninvasively by means of bioengineering tools. Skin elasticity, hydration, skin blood flow and skin surface pattern show age-related changes reflecting the damage of cutaneous structures involved. Impairment and degeneration of elastic and collagen networks are responsible for the progressive decrease in skin elasticity recorded during aging. Reduction in blood flow and water supply with probably defective stratum corneum binding result in reduced stratum corneum water content and transepidermal water loss. Morphological changes such as increased skin roughness, pigmentation and alteration of skin surface pattern appearing from the age of 30 years onwards may be investigated at a subclinical level allowing the detection of early signs of aging.

Enhancement of propranolol hydrochloride and diazepam skin absorption in vitro: effect of enhancer lipophilicity

The enhancement of model hydrophilic (propranolol hydrochloride) and lipophilic (diazepam) drug penetration across rat and hairless mouse skin in vitro has been studied. Preliminary experiments established that most n-alkanes having chain lengths of between 7 and 16 promote the flux of both drugs. For propranolol, enhancement varied parabolically with carbon number; for diazepam, heptane was ineffective and all others were essentially equipotent. Enhancement by n-nonane was then compared with that by n-nonanol. Propranolol flux was increased by both enhancers, whereas diazepam penetration was not affected by the less lipophilic alcohol. The enhancement of propranolol by n-nonane and n-nonanol was examined as a function of adjuvant concentration in the applied formulation. Maximum increases in maximum penetration rates of 6.5-fold (n-nonane) and 8.2-fold (n-nonanol) were determined. As expected, the enhancement was saturable, indicative of a maximally perturbed stratum corneum. Finally, the penetration enhancing abilities of six monoterpenes were assessed. The purely hydrocarbon analogues promoted both propranolol and diazepam transport to an extent similar to that of n-nonane. The terpenes with hydrogen-bonding ability, however, only enhanced propranolol flux (at a level comparable to n-nonanol). While the data reported do not directly reveal mechanistic information on percutaneous penetration enhancement, they do provide a starting point for the rational investigation of interrelationships between drug, enhancer, and skin. Such information is clearly essential for the optimization and exploitation of transdermal drug delivery.

Effect of low-concentration sodium lauryl sulfate on human vulvar and forearm skin. Age-related differences

The reactivity of forearm and vulvar skin to low-concentration sodium lauryl sulfate (SLS) was studied in 20 healthy women, 10 before and 10 after menopause. SLS at concentrations of 0.1%, 0.5% and 1.0% was applied to the forearm and labium majus for 24 hours. Skin changes were monitored with transepidermal water loss (TEWL), capacitance (CAP) (as an indicator of stratum corneum hydration) and visual scoring (VS). In forearm skin, irritant dermatitis developed in most subjects, as indicated by a VS and TEWL increase, with the reaction in premenopausal women significantly more intense than in postmenopausal women. In vulvar skin, however, irritant reactions were not observed. CAP increased significantly in the forearm of premenopausal but not postmenopausal women, whereas it decreased significantly in postmenopausal vulvar skin. Thus, vulvar skin was less reactive to SLS at low concentrations than was forearm skin. However, SLS did affect vulvar skin stratum corneum hydration. The irritant response in the forearm decreased with age for all parameters studied, whereas in vulvar skin age-related differences in irritant reaction were limited to stratum corneum hydration.

Optimization of topical therapy: partitioning of drugs into stratum corneum

To optimize a topical formulation for therapeutic effect generally implies that the flux of drug into the skin be maximized. This requirement means that the product of drug concentration in the vehicle (Cv) and drug partition coefficient (PC) between stratum corneum (SC) and vehicle be as large as possible. While Cv is a formulation variable which can be easily manipulated up to the drug's saturation solubility, PC is a parameter that is difficult to predict a priori. However, there is no question that an ability to evaluate PC would greatly facilitate the efficient screening of drugs and formulations. We have measured the SC/water and SC/isopropylmyristate (a model lipophilic vehicle) PCs of seven drugs; acitretin, progesterone, testosterone, diazepam, estradiol, hydrocortisone, and caffeine, SC/water PCs were determined as a function of the following variables: (i) initial drug concentration in the vehicle, (ii) length of equilibrium, (iii) SC source and preparation technique, and (iv) SC delipidization. The data obtained were reproducible and physicochemically consistent, and they show that useful partitioning information from both aqueous and nonaqueous vehicles can be obtained with the biological tissue of greatest relevance. The SC/water PCs of the steroids were in reasonable agreement with previous measurements. A facile approach to an integral determinant of formulation optimization is suggested, therefore, by these observations.

Cutaneous pharmacodynamics of transdermally delivered isosorbide dinitrate

Laser doppler velocimetry (LDV) has been used to assess the cutaneous pharmacodynamics of isosorbide dinitrate (ISDN) following transdermal delivery of the drug from prototypal patches. The delivery systems, which were saturated with ISDN, (a) produced various degrees of skin occlusion and (b) spanned a six-fold range of adhesiveness. The patches were applied to the ventral forearm skin of 10 healthy volunteers and the local ISDN-induced increase in local skin blood flow was determined using LDV by locating the probe in a central hole in the delivery system. Measurements were made for 1.5 hr and the pharmacodynamics were quantified by (i) the maximum LDV response and (ii) the area under the LDV response versus time curve. These parameters were not sensitive to patch occlusivity. They were significantly (P less than 0.01) dependent on patch adhesiveness, though, and decreased with increasing adhesion. Although this observation suggested that ISDN diffusion through the adhesive could determine, at least in part, the rate of drug delivery, it was subsequently demonstrated that ISDN release (in vitro, into a perfect "sink") was unaffected by the level of cross-linking in the adhesive polymer. Because the drug was present in all systems at unit thermodynamic activity, these results cannot be explained on the basis of altered ISDN partitioning at the device-stratum corneum interface. We speculate that the in vivo-in vitro discrepancy may be due to the efficiency of skin contact achieved by different adhesives: that is, the more adhesive, less flexible systems make poorer contact with the skin surface, thereby decreasing the effective surface area of drug delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbiology of specialized skin: the vulva

Human vulvar skin is an example of specialized skin. This is not only true for its gross and microscopic anatomy and physiology, but also for its microbiology. To the microbiologist, the vulva consists of several distinct ecotopes. These are defined by the physical factors, especially occlusion, nutrient factors, and by the close proximity to the vagina, the urethra, and the anus, which may result in contamination with the flora typical for those sites. Of the vulva ecotopes, only the labia majora have been seriously studied. The microbial flora of the labia majora is characterized by a high density of microorganisms, as is typical for occluded areas of the body, by the presence of organisms common for intertriginous skin such as gram-negative rods, and by the carriage of organisms unique for the vulva and probably related to urethral and vaginal flora such as the nonpathogenic neisseria, lactobacilli, and Gardnerella vaginalis. Finally, the labia majora skin is a preferred site of Staphylococcus aureus carriage that can be of clinical and epidemiological relevance.

Percutaneous absorption and skin decontamination of PCBs: in vitro studies with human skin and in vivo studies in the rhesus monkey

Knowledge of the entry of polychlorinated biphenyls through the skin into the body and subsequent disposition aids estimation of potential for human health hazard. [14C]Aroclor 1242 and [14C]Aroclor 1254 were separately administered intravenously and topically to rhesus monkeys. Following iv administration, 30-d excretion was 39.4 +/- 5.9% urine and 16.1 +/- 0.8% feces (total 55.5 +/- 5.1%) for Aroclor 1242, and 7.0 +/- 2.2% urine and 19.7 +/- 5.8% feces (total 26.7 +/- 7.5%) for Aroclor 1254. Mineral oil and trichlorobenzene are common PCB cosolvents in transformers. Skin absorption of Aroclor 1242 was 20.4 +/- 8.5% formulated in mineral oil and 18.0 +/- 3.8% in trichlorobenzene (p greater than .05). Absorption of Aroclor 1254 was 20.8 +/- 8.3% in mineral oil and 14.6 +/- 3.6% in trichlorobenzene (p greater than .05). PCBs are thus absorbed through skin, and excretion from the body is slow. Vehicle (trichlorobenzene or mineral oil) did not affect percutaneous absorption. In vitro skin absorption in human cadaver skin did not correlate with in vivo findings. This was due to lack of PCB partition from skin into the water receptor fluid, even with addition of 6% Oleth 20 (Volpo 20) solubilizer. Skin decontamination of PCBs showed soap and water to be as effective as or better than the solvent ethanol, mineral oil, and trichlorobenzene in removing PCBs from skin. There is a dynamic time lapse for PCBs between initial skin contact and skin absorption (irreversible removal). Thus initially most PCBs could be removed from skin, but this ability decreased with time to the point where at 24 h only about 25% of the initial PCB skin dose could be recovered with skin washing.

Cutaneous sodium lauryl sulphate irritation potential: age and regional variability

To investigate differences in response to irritation according to age and site seven young-adult and eight elderly females were exposed to 0.25% sodium lauryl sulphate (SLS) under patch-test occlusion for 24 h. Ten anatomical regions were tested: forehead, upper arm, volar and dorsal forearm, postauricular, palm, abdomen, upper back, thigh, and ankle. The skin responses were evaluated 24 h post-patch removal by visual scoring and by transepidermal water loss measurements (TEWL). Non-treated symmetrical anatomical regions served as controls. SLS induced a mild erythematous reaction on most anatomical regions except the palm and TEWL was significantly increased as compared with controls. The elderly group demonstrated significantly less susceptibility to SLS-induced irritation for most regions of the body as indicated by visual scores and TEWL measurements. In addition, evaluation of the stratum corneum water content following SLS irritation demonstrated lower responses in the old age group for most regions. The thigh had the highest reactivity and the palm the lowest, in both age groups. These data suggest that young adult skin is more sensitive to SLS than old skin and that SLS irritation varies considerably with respect to region. Moreover, objective TEWL measurements seem to be a better indicator of irritant susceptibility, especially in the elderly, than clinical evaluation by visual scoring.

The relationship between pKa and skin irritation for a series of basic penetrants in man

For a series of bases, which penetrate through human skin in vitro at similar rates (0.056-0.49 microM/cm2/hr), penetrant pKa is shown to correlate with erythema, edema, and color meter readings. As estimates of irritation, erythema, edema, and redness measurements are highly linearly correlated. For the selected series, irritation becomes significant for bases with a pKa greater than 8. The irritation potential of acids with pKa less than or equal to 4 has been previously reported; pKa appears highly predictive of acute skin irritation for acids and bases in man.

Irritant effect of a model surfactant on the human vulva and forearm. Age-related differences

The reactivity of forearm and vulvar skin to sodium lauryl sulfate (SLS) was studied in two groups of 20 healthy women each, 10 before and 10 after menopause. Vulvar skin was less reactive to SLS in both low and high concentrations than was forearm skin. Transepidermal water loss measurement did not seem to be an indicator of irritant dermatitis in vulvar skin. Capacitance measurements, reflecting changes in skin hydration, seemed to be more suitable for monitoring vulvar irritant dermatitis. Age-related differences in irritant reaction were more apparent in low-grade irritant dermatitis induced by low concentrations of SLS than in intense reactions to higher SLS concentrations.

Irritation factors of sodium hypochlorite solutions in human skin

The recommended concentration for patch testing with sodium hypochlorite [NaOCl] (bleach) is 1%, generally obtained by diluting commercial bleach. In doing so, other active (potentially irritant) components of bleach, especially hypochlorous acid [HOCl] and sodium hydroxide [NaOH], are neglected. Magnitudes of potential irritant species other than NaOCl, such as alkalinity, are ordinarily not labeled on the product, though they may vary considerably between brands. Thus, patch testing with 1% hypochlorite obtained by diluting different brand bleaches can potentially elicit non-specific irritant responses, also depending upon the test volume applied. In this study, skin irritation induced by 24-h patch testing with 20 microliters or 100 microliters, with constant NaOCl concentration (1%) and different NaOH concentrations (0.01-1.0%), was studied in adult human volunteers, by means of visual scores and skin color reflectance measurements. No irritation was elicited by application of 20 microliters 1% OCl-, independent of the NaOH concentration. However, all solutions induced significant irritation in a volume of 100 microliters. Skin reactions did not show a straight pH dose response, a maximum reaction being seen to the solution containing 0.1% NaOH. Skin surface pH values had increased when monitored immediately after removal of the patch material. However, 24 h later, baseline values were again reached at most sites, demonstrating an efficient buffering capacity of human skin, even after challenge with alkaline solutions of pH 13.4. We suggest that a non-irritant concentration for diagnostic patch testing for allergic contact dermatitis with an aluminum chamber, using 17 microliters to 20 microliters test volume, could be as high as 1% NaOCl and 1% NaOH.

The practical use of methotrexate in psoriasis

Psoriasis is an inflammatory disease of the skin associated with increased epidermal proliferation. The aetiology of the disease is unknown, but there seems to be a genetic predisposition. The goal of therapy in the treatment of psoriasis is to decrease the rate of epidermal proliferation and the underlying inflammation. Topical application of steroids and coal tar are the therapies of choice; however, for those patients with severe recalcitrant psoriasis who have failed conventional topical therapy methotrexate is an established alternative. The use of methotrexate in psoriasis is limited by its toxicity, and proper patient selection and close monitoring are essential in achieving good clinical response. The dosage used should be the lowest that will maintain the patient in comfort, not necessarily that which produces total resolution. Caution should be exercised when other agents are used concurrently with methotrexate, and possible drug interactions should be identified as these may influence the effectiveness and toxicity of methotrexate therapy. The common side effects associated with the use of methotrexate in psoriasis include bone marrow suppression, gastrointestinal symptoms and hepatotoxicity. Liver damage is a major concern in long term methotrexate therapy and thus liver biopsies are warranted to monitor any pathological changes. The drug is a known teratogen and should be avoided in pregnant patients. Women of childbearing age should use reliable contraception during therapy. Patients should be made aware of the signs and symptoms of methotrexate toxicity and inform their physicians promptly as most adverse effects can be ameliorated with appropriate dosage adjustment. Methotrexate will continue to play a major role in the treatment of psoriasis and it is thus important that it be used safely.

Sodium lauryl sulfate-induced irritant contact dermatitis in vulvar and forearm skin of premenopausal and postmenopausal women

Reactivity of the skin of the forearm and labia majora to three concentrations (2%, 3%, 5%) of sodium lauryl sulfate was studied in 20 healthy women, 10 premenopausal and 10 postmenopausal. Patches with the irritant were applied on day 0 for 24 hours. Skin changes were monitored by visual scoring and by the measurement of transepidermal water loss and capacitance as indicators of stratum corneum hydration on days 2, 3, 7, and 10. In forearm skin, irritant dermatitis developed in the majority of subjects as indicated by visual scoring and increase of transepidermal water loss. These changes were not significantly dependent on the concentration of sodium lauryl sulfate. In labia majora skin, irritant dermatitis developed in 50% of the women as determined by visual scoring; however, because of the pigmentation, visual scoring readings were less reliable in labia majora skin. Transepidermal water loss did not increase, but a significant and immediate decrease in capacitance was noted in labia majora skin. In forearm skin, postmenopausal women reacted less frequently and more slowly to sodium lauryl sulfate than premenopausal women whereas no age-related differences were observed in reaction of the vulvar skin. It is concluded that labia majora skin is not more reactive to sodium lauryl sulfate than forearm skin and that capacitance is more sensitive than transepidermal water loss in monitoring vulvar irritant dermatitis. Age-related differences in irritant reaction are apparent in the forearm, but not the vulva.

Percutaneous absorption of [14C]DDT and [14C]benzo[a]pyrene from soil

The objective was to determine percutaneous absorption of DDT and benzo[a]pyrene in vitro and in vivo from soil into and through skin. Soil (Yolo County 65-California-57-8; 26% sand, 26% clay, 48% silt) was passed through 10-, 20-, and 48-mesh sieves. Soil then retained by 80-mesh was mixed with [14C]-labeled chemical at 10 ppm. Acetone solutions at 10 ppm were prepared for comparative analysis. Human cadaver skin was dermatomed to 500 microns and used in glass diffusion cells with human plasma as the receptor fluid (3 ml/hr flow rate) for a 24-hr skin application time. With acetone vehicle, DDT (18.1 +/- 13.4%) readily penetrated into human skin. Significantly less DDT (1.0 +/- 0.7%) penetrated into human skin from soil. DDT would not partition from human skin into human plasma in the receptor phase (less than 0.1%). With acetone vehicle, benzo[a]pyrene (23.7 +/- 9.7%) readily penetrated into human skin. Significantly less benzo[a]pyrene (1.4 +/- 0.9%) penetrated into human skin from soil. Benzo[a]pyrene would not partition from human skin into human plasma in the receptor phase (less than 0.1%). Substantivity (skin retention) was investigated by applying 14C-labeled chemical to human skin in vitro for only 25 min. After soap and water wash, 16.7 +/- 13.2% of DDT applied in acetone remained absorbed to skin. With soil only 0.25 +/- 0.11% of DDT remained absorbed to skin. After soap and water wash 5.1 +/- 2.1% of benzo[a]pyrene applied in acetone remained absorbed to skin. With soil only 0.14 +/- 0.13% of benzo[a]pyrene remained absorbed to skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Frictional properties of human skin: relation to age, sex and anatomical region, stratum corneum hydration and transepidermal water loss

Differences in the dynamic skin friction coefficients (mu) were investigated with respect to age, sex, and anatomical region. A total of 29 volunteers consisting of seven young females, seven old females, seven young males, and eight old males participated in the study. Measurements were obtained from II anatomical regions, namely, the forehead, upper arm, volar and dorsal forearm, postauricular, palm, abdomen, upper and lower back, thigh, and ankle. The friction data were compared with stratum corneum hydration and transepidermal water loss (TEWL). The dynamic friction coefficient did not vary significantly between age and sex groups but varied considerably among the anatomical regions of the body. The forehead and postauricular had the highest mu (0.34 +/- 0.02) while the abdomen had the lowest (0.12 +/- 0.01); the remaining regions had an average mu value of 0.21 +/- 0.01. Similarly, no sex differences were observed for TEWL and stratum corneum hydration. Capacitance was only significantly lower on the palms of the elderly. Regional differences showed a higher state of hydration on the forehead and postauricular as well as the upper arm, upper and lower back when compared with the volar forearm. TEWL was generally lower in the elderly on all anatomical regions except the postauricular and palm. A significant correlation was established between mu and capacitance for most regions. Between mu and TEWL significant correlation was observed only on the palm and thigh. These findings suggest that frictional properties of skin are dependent on more than water content or non-apparent sweating and the role of sebum secretion is suggested as one possible factor.

Contact dermatitis: prognosis, risk factors, and rehabilitation

This article reviews the prognosis for irritant and allergic contact dermatitis and occupational and nonoccupational contact dermatitis. Factors adversely affecting prognosis are discussed. Rehabilitation of the patient with disabling contact dermatitis is considered. The importance of the various risk factors for contact dermatitis are reviewed.

An international survey on the prognosis of occupational contact dermatitis of the hands

Prognosis is a crucial topic in contact dermatitis. We recently reviewed the extensive literature on the prognosis of contact dermatitis. The majority of patients in these studies had persistent dermatitis. Job changes usually did not lead to a significant improvement for most patients with occupational contact dermatitis. We performed a worldwide survey of colleagues with expertise in treating patients suffering from occupational contact dermatitis of the hands. Of 65 experts, 51 returned questionnaires for analysis. 67% of European and 29% of respondents from Sweden, Denmark, Finland, United States of America, Canada, and Mexico stated that more than 75% of workers with severe hand dermatitis required a job change. 78% of the respondents found that chromate and 57% found that nickel allergy were associated with the worst possible prognosis. 98% felt that barrier creams were no more effective than bland emollients in the prevention of hand dermatitis.

Elastic properties of human skin: relation to age, sex, and anatomical region

Using a recently developed noninvasive, in vivo suction device for measuring skin elasticity, we evaluated age, sex, and regional differences in the viscoelastic properties of skin. A total of 33 volunteers participated in the study consisting of (a) 8 young females, (b) 9 old females, (c) 8 young males and (d) 8 old males. Measurements were performed on 11 anatomical regions; three different loads were applied: 100, 200, and 500 mbar. The parameters used were: immediate distension (Ue); delayed distension (Uv); immediate retraction (Ur); and, final deformation (Uf). To compare between subjects and anatomical regions, relative parameters independent of skin thickness were calculated: Uv/Ue, the ratio between the viscoelastic properties of skin and immediate distension, and Ur/Uf, which measures the ability of the skin to regain its initial position after deformation. Generally, Uv/Ue increased while Ur/Uf decreased with aging. Responses were variable with respect to load applied. Variability within anatomical regions was also noted. However, differences between the sexes were not statistically significant for most regions. These findings are in congruence with earlier studies suggesting the differences are mainly attributable to alterations in the elastic fiber network. This procedure provides a simple, quantitative assessment of elastic properties of the skin. Its application may help in future investigations of other connective tissue disorders.

The prognosis of contact dermatitis

This article reviews the prognosis of contact dermatitis, particularly of occupational contact dermatitis. Most studies document a poor prognosis for occupational and nonoccupational contact dermatitis. The prognoses of occupational and nonoccupational contact dermatitis, irritant contact dermatitis, and allergic contact dermatitis are similar. Only a minority of studies on the prognosis of occupational contact dermatitis have found that a job change by the affected worker leads to clearing of the dermatitis. Dermatologic and nondermatologic factors associated with a poor prognosis are discussed.

Ranking of surfactant skin irritancy in vivo in man using the plastic occlusion stress test (POST)

Irritant effects and disturbance of water-holding capacity induced by surfactants were investigated using the plastic occlusion stress test (POST) technique. 4 surfactants (sodium lauryl sulphate (SLS), sorbitan monolaurate, cocoamidopropyl betaine and benzalkonium chloride) and an amphoteric/nonionic (A/N) mix were investigated. 1 x daily for 3 days, test surfactants were applied to marked sites (open) on the volar forearm. After 24 h occlusion with a plastic chamber on the 4th day, skin surface water loss (SSWL) (g/m2h) was recorded continuously for 25 min with an evaporimeter. The differences between the surfactants were statistically significant (Friedman's test p less than 0.01). SLS and the A/N mix revealed significant differences compared to the other compounds (p less than 0.05), both in decay constants and in values recorded at the beginning and at the end of the decay curve. The study suggests a mechanism for the high irritant potential of sodium lauryl sulphate compared to other surfactants: sorbitan monolaurate and benzalkonium chloride seem to influence (at the concentrations tested) to a lesser extent the water-holding capacity of the stratum corneum. The clinical and biological relevance of these observations requires long-term clinical correlations with final product use tests.

Partitioning of chemicals into human stratum corneum: implications for risk assessment following dermal exposure

Assessment of the health hazard associated with chemical contamination of the skin is a complex problem of occupational and environmental relevance. A particularly important question is to what extent can the skin permeability of a given compound be predicted from simple experiments. The literature on percutaneous absorption identifies two key observations: (i) the stratum corneum (SC), the skin's outermost layer, is the major barrier to chemical transport, and (ii) there are qualitative correlations between penetrant permeability and various oil/water partition coefficients (PCs). To obtain more quantitative predictions of permeation, we have evaluated SC/water and SC/isopropyl myristate (IPM, a model lipophilic vehicle) PCs of (a) para-substituted phenols of diverse physicochemical properties (4-acetamido-, 4-cyano-, 4-iodo-, and 4-pentyloxyphenol), (b) polychlorinated biphenyls (54%), and (c) 1,1,1,-trichloro-2,2-bis(p-chlorophenyl)ethane. Partition coefficients were determined as a function of the following variables: length of equilibration, initial drug concentration in the vehicle, SC delipidization, and SC source and preparation technique. The data demonstrate that reproducible partitioning can be obtained using the biological tissue of greatest relevance, and that the pattern of behavior observed, for the two different vehicles studied, is compatible with physicochemical expectations. We suggest that the PC values measured may be useful predictors of in vitro and in vivo skin transport and valuable assets, therefore, in the evaluation of risk following dermal exposure.

Multiple parameter assessment of vulvar irritant contact dermatitis

Transepidermal water loss (TEWL), capacitance, pH, blood flow and color reflectance were evaluated for quantifying the irritant response of vulvar and forearm skin to 3% sodium lauryl sulfate in 9 healthy premenopausal women. TEWL, capacitance, pH, blood flow, and all parameters of color reflectance changed significantly in forearm irritant dermatitis. In vulvar irritant dermatitis, however, significant changes were observed only for blood flow and the color reflectance parameters a* and b*. Using the combination of TEWL, capacitance and blood flow, forearm irritant dermatitis was detected with a sensitivity of 84% and a specificity of 100%. In this study, the best combination of parameters to detect vulvar irritant dermatitis was pH, blood flow, a* and b*, which had a sensitivity of 78% and a specificity of 75%. It is concluded that available bioengineering techniques are less suitable to quantify irritant dermatitis in the vulva than in the forearm.