Baseline water loss and cholinergic sweat stimulation in atopic dermatitis: a gravimetric measurement of local skin water loss

Treatment of hyperhidrosis with Botox (onabotulinumtoxinA): Development, insights, and impact

Hyperhidrosis (chronic excessive sweating) may substantially affect an individual's emotional and social well-being. Therapies available before onabotulinumtoxinA were generally topical, with limited effectiveness, application-site skin reactions, and frequent, time-consuming treatments. Intradermal injection of onabotulinumtoxinA to treat sweat glands arose as a novel therapeutic approach. To develop this treatment, appropriate dosing needed to be established, and training on administration was required. Further, no previous scale existed to measure the effects of hyperhidrosis on patients' lives, leading Allergan to develop and validate the 4-point Hyperhidrosis Disease Severity Scale (HDSS), which measures the disease's impact on daily activities. The onabotulinumtoxinA clinical development program for hyperhidrosis included 2 double-blind, placebo-controlled pivotal trials, immunogenicity studies, long-term studies of safety and efficacy, and quality of life assessments. In Europe and North America, the primary efficacy measures were, respectively, axillary sweat production measured gravimetrically and HDSS improvement. Compared with placebo, onabotulinumtoxinA treatment significantly reduced axillary sweat production and axillary hyperhidrosis severity, as measured by a 2-point or greater reduction on the HDSS. The effects of onabotulinumtoxinA occurred rapidly, within 1 week after injection, and lasted ≥6 months. Treatment with onabotulinumtoxinA was associated with significant quality of life improvements based on Short Form-12 physical and mental component scores. The Hyperhidrosis Impact Questionnaire also indicated greater treatment satisfaction, reduced negative impact on aspects of daily life, and improved emotional well-being with onabotulinumtoxinA versus placebo. The clinical development program and subsequent clinical experience showed that onabotulinumtoxinA treatment for hyperhidrosis was well tolerated with no new safety signals, and led to greater disease awareness.

Stress and atopic dermatitis

Atopic dermatitis (AD) is a complex disease traditionally involving interaction of genetic, environmental, and immunologic factors. Recent studies suggest psycho-neuro-immunologic factors and emotional stress are important in its evolution. The observations that internal (bacterial infections) or external (psycho-logic) stressors may induce AD flares is explained by studies showing that stress impairs the skin barrier function and favors a shift in immunity toward a T helper type 2 cell/allergic response. Furthermore, those with AD appear to have an inherited hypothalamic deficiency that impairs normal hypothalamic-pituitary-adrenal axis function. Neuropeptides released in the skin may also mediate neurogenic inflammation, including mast cell degranulation. AD causes significant stress and impaired quality of life in patients and their family members. Psychologic and stress-reduction interventions were recently shown to improve patient well-being, and to significantly improve cutaneous manifestations.

Do training-dependent differences in perspiration exist between healthy and atopic subjects?

Sweating (perspiratio sensibilis) serves predominantly for thermoregulation and is triggered, among other stimuli, by physical stress. Although consensus on sex-dependent differences in sweating has not been reached so far and recent studies revealing abnormal diminution of the sweating capacity in atopic subjects are mainly based on heat exposure experiments, the influence of endurance training on perspiration in atopics has not yet been evaluated. Using a special sweat collector device reliable even during intensive body movement, we compared the sweat production of age-matched male and female healthy controls (14 m, 10 f) to that of in-patients with atopic eczema (AE: 14 m, 10 f) during and 5 min after physical exercise (30 min) with a bicycle ergometer under standardized experimental conditions. The individual stress limit was determined by a previous endurance test including repeated lactate blood level measurements and continuous heart rate control. Informed consent was obtained from every participant in the study. One half of both the patients and the controls underwent three week endurance training, and the preceding sweat measurements were repeated in all patients and controls after the training period under identical conditions. On average, the healthy males perspired nearly twice as much as the corresponding females (p < 0.0016). Highly significant mean differences of maximum sweat secretion rates were also found between the atopics and the controls. Healthy individuals of both sexes perspired nearly three times as much as did the patients with AE (males: p < 0.0004; females: p < 0.00009). Among the atopics there were remarkable, yet statistically insignificant, sexual differences in sweat production. After three weeks, sweating rates were similar to the initial ones in the training group as well as in the non-trained control group. Gender differences in perspiration do not only exist between healthy males and females but also in patients with atopic skin disorder, yet the latter ones at significantly lower levels as compared to healthy control subjects. No influence of a three-week-exercise phase on sweat secretion in atopics and controls could be proven. For designing further studies on intra- or intersexual differences of drug-independent perspiration, standardized physical stress can be recommended as an experimental prerequisite for sweat measurements.

Sweat gland function as a measure of radiation change

BACKGROUND

Radiotherapy may result in dryness of the skin even when no other change can be detected. We describe a system for recording the electrical conductance of skin as a measure of sweat gland function.

PATIENTS AND METHODS

In 22 normal volunteers close agreement was obtained between measurements obtained from comparable sites on both sides of the chest. Measurements were subsequently made in 38 patients treated by radiotherapy to one side of the chest for tumours of the breast or lung using one of five different fractionation schedules. Simultaneous readings were obtained from both sides of the chest with the non irradiated side acting as a control.

RESULTS

A dose response relationship was demonstrated: five patients who received the equivalent total dose of 15 Gy in 2-Gy fractions showed no change in conductance. Sixteen out of 23 who received an equivalent total dose of 42-46 Gy in 2-Gy fractions had a greater than 22% reduction in mean skin conductance compared with that of the control areas despite the skin appearing normal in the large majority. Marked changes in skin conductance were seen after higher total doses. In a prospective study 18 women receiving breast irradiation underwent weekly readings during treatment. A mean reduction of 40% in skin conductance was noted by the end of the second week of treatment prior to any clinical evidence of radiation change. Skin conductance returned to normal in 44% of patients by 6 months. In the remainder, those patients who showed the greatest reduction in skin conductance during treatment demonstrated the least recovery.

CONCLUSIONS

Changes in sweat gland function can be detected and quantified in skin which may otherwise appear normal. Differences may so be demonstrated between areas treated using different fractionation schedules and the method may be applied to the detection during radiotherapy of unusually sensitive patient.

Sweating response to moderate thermal stress in atopic dermatitis

The local sweating response to thermal stress (mean ambient temperature 33 degrees C) was assessed under resting conditions on the non-eczematous back skin of 26 young men with atopic dermatitis (AD) and in 22 non-atopic controls with other dermatoses. The baseline (transepidermal) water loss was separately determined at room temperature (mean 23.6 degrees C) to calculate the pure sweat loss. A gravimetric collecting method was used for the measurements at 40, 60 and 80 min. In the heated room the sweat loss in AD patients was significantly lower at all time intervals. The cumulative sweat loss was 50-60% lower in AD patients than in the controls (P less than 0.02). Subjects with dry AD skin had a lower sweat loss than subjects with normal-looking skin. Compared with controls the sweat loss in AD patients was lowest at 40 min, suggesting a retarded sweating response. Half of the patients with AD and half of the controls had active participation in sports, and showed a greater sweat loss compared to the non-sporting subjects in the same group.

Adrenaline-induced local sweating and vasoconstrictive responses in atopic skin

Sweating and vasoconstrictive responses to intradermal injections of adrenaline were studied in the normal-looking back skin of young adult males with atopic dermatitis (AD) and in non-atopic controls using five concentrations of adrenaline, and further in a subgroup of subjects with dry-looking AD skin using two concentrations of adrenaline. The sweating responses were measured with an evaporimeter and the area of blanching determined with planimetry. The maximal sweating response in the AD group was elicited with the suprathreshold concentration of 5 x 10(-6) mol/l and in the non-atopic group with a 10-fold higher concentration. At the three higher concentrations the sweat rates levelled out in both groups and remained at a lower level in AD subjects. The sweating responses in dry-looking AD skin were lower than in non-atopics (P less than 0.001) and were also lower than in those with AD normal-looking skin (P less than 0.05) with both concentrations. In contrast to sweating, the vasoconstrictive reactions showed similar dose-dependent increases with all tested concentrations in AD patients with normal-looking skin and in the non-atopic controls. In patients with dry AD skin the vasoconstrictive responses were also similar to those in non-atopic controls.