The skin is the largest multifunctional organ of the human body with a total surface area of about 2 m2. The skin is composed of a set of complex organs, which provide protection and sense functions. As a physical barrier, the skin protects the body from environmental threats such as temperature, pathogens, and mechanical, and chemical impacts by acting as a selective barrier. From a sensory standpoint, the skin has several receptors, which provide afferent information related to pain, touch, and temperature . The skin has three layers; epidermis, dermis, and the subcutaneous layer (hypodermis). The stratum corneum is the uppermost part of the epidermis and consists of dead, keratinized cells.
Healthy skin can be characterized by its biophysical characteristics, such as skin moisture, sebum (oil) content, and pH. The normal level of skin (stratum corneum) moisture is influenced by various factors such as the amount of supplied water from the viable epidermis, dermis, and sebaceous glands, and also the stratum corneum's ability to accumulate water, and the volume of water lost through evaporation . Moreover, the value of skin moisture can also be influenced by the type of consumed foods . The skin sebum level is linked to individual characteristics and environmental conditions. Sebum production is dependent on the location, density, and activity of sebaceous glands . Normal levels of sebum are associated with a high level of moisture . Healthy skin has a pH value between 4.0 and 6.0. The normal pH value takes part in the maintenance of a normal level of skin moisture . An increase in the skin pH leads to activation of cathepsins, breaking down of filaggrin, which decreases the natural moisturizing factor . Also, an increase in transepidermal water loss is related to increased pH values .
Biophysical characteristics of the skin could also be a significant indicator of skin diseases. For instance, atopic dermatitis is associated with higher skin pH , and lower skin moisture and sebum . In addition, a positive correlation between atopic dermatitis severity and pH values is observed in various studies . Moreover, acne is related to increased skin pH , and sebum . Therefore, understanding the biophysical properties characteristics of the skin might be useful in dealing with skin diseases with a proper approach.
To the best of our knowledge, no data are available on the skin biophysical parameters of patients with coronavirus. Therefore, in the present study, skin moisture, sebum and pH were measured to investigate the association between skin biophysical properties and coronavirus patients for three days in a row. Without any doubt, the body temperature, the primary test that is performed, of patients who had confirmed coronavirus symptoms was significantly higher than that of the unaffected controls. Therefore, this study hypothesized that an increase in skin temperature in coronavirus patients leads to altering its biophysical parameters such as skin moisture, sebum, and pH for three consecutive days of hospital stay.
A total of 30 coronavirus patients (14 males and 16 females), age range 27–90 years (mean 64 years) were enrolled in the study. All the recordings were performed at the coronavirus hospital in Duhok city under standard working conditions (T= 20-23 °C and relative humidity 40-60%).
Skin moisture, sebum content, pH, and temperature data were recorded from patients for three days in a row. It is worth noting that severe cases were not included in this study. All precautionary measures related to coronavirus were considered during the data collection.
Skin moisture, oil (sebum), pH, and temperature were recorded by using three different portable instruments. An SK-IV digital moisture monitor (Riuty, China) was employed to measure skin moisture and oil. It is based on bioimpedance technology and could measure the skin moisture within the range of 0-99.9%. Skin pH was measured by employing a pH meter with an accuracy of ±0.1 pH, using a high precision, corrosion resistant probe. Lastly, skin temperature was monitored by utilizing an infrared thermometer device (EFT-162-China).
Differences among skin moisture, oil and pH recordings were statistically analyzed by using the one-way repeated analysis of variation (ANOVA) followed by post hoc multiple pairwise comparisons using Sidak correction. The statistical analyses were done by employing IBM SPSS Statistics and the 0.05 level of confidence was used to define statistical significance.
Informed consent has been obtained from all individuals included in this study.
The protocol has been complied with all the relevant national regulations, institutional policies and in accordance with the Helsinki Declaration, and the study protocol was approved by the director of the coronavirus hospital in Duhok city.
Skin moisture data recorded during three days for all patients are presented in Figure 1. It can be seen that there are variations in the skin moisture of patients. In addition, on average, skin moisture was increased by comparing the second (44.03%) and third days (44.82%) to the first one (42.43%). Moreover, statistical analysis with ANOVA tests showed significant (
Shown in Figure 2 is the skin sebum content computed for each patient during the three days.
According to the data seen in the figure, skin sebum content values for the patients are slightly changed with respect to days. In addition, on average per 30 patients, skin sebum content is increased from 9.12 (on the first day) to 9.19 (on the second day), and 9.66 (on the third day). However, when the obtained data from over 30 patients were analyzed with ANOVA tests, non-significant (
The results for skin pH with respect to the three days are presented in Figure 3. Variations in values of skin pH are also observed. Moreover, fluctuations are seen in average values of skin pH, but comparing the third day (4.68) to the first day (4.62), it is slightly increased. However, when the statistical analysis with post hoc pairwise multiple comparison tests was employed, non-significant (
Fluctuations are also seen (Figure 4) in the skin temperature of patients during the three days. In addition, highly significant (
This study aimed at recording biophysical parameters of the skin of coronavirus patients for three days in a row. According to the initial results, the biophysical characteristics of the coronavirus patients changed during the period of the study recordings.
Skin moisture, or the retention of water in the outermost layer of the skin known as the stratum corneum, which regulates skin inflammation, proliferation, and differentiation [12, 13], was significantly increased. This might be due to an increase in skin temperature and sweating, which consequently leads to increases in skin hydration. Jung
Small variations are obtained in the skin sebum content. According to the observed findings, skin sebum on average was slightly increased compared to the first day, but these results were statistically non-significant (
There were fluctuations in the skin pH of patients over the three days of monitoring. On the second and third days, it increased. The skin acidic milieu is necessary for epidermal permeability barrier homeostasis, restoration of the disrupted barrier, and the skin nonspecific antimicrobial defense [18, 19]. The reduction in skin pH on the third compared to the second day, may be due to increased body temperature and sweating. Jung
Skin temperature monitoring plays an important role in the preliminary screening of coronavirus patients. Although on average skin temperature did not exceed the normal range, the temperature of patients on average rose significantly (
The current study is the first that monitored the variations in biophysical properties of the skin for hospitalized coronavirus patients. Yet, two limitations must be considered. First, we tried to measure the variables for the first three days of symptoms appearing in patients infected with the coronavirus; however, controlling the admission of patients to the hospital as soon as symptoms appear is very difficult. Independent replication over longer periods with larger samples is needed to assess the strength of the directionality of the effects identified here. Second, we analyzed the data based on the provided treatment protocol at the hospital, and no information on the treatment provided to patients was obtained.
Overall, we observed that skin moisture, sebum content, pH, and skin temperature increased over three days in a row of recordings. Changes in both skin moisture and temperature were significant, but changes in skin sebum and pH were non-significant. Skin biophysical parameters could be further investigated to be used as a useful indicator for the health conditions of coronavirus patients in clinical settings.
Algorithms for reconstruction of impedance spectra from non-uniformly sampled step responses Monitoring the skin biophysical parameters among coronavirus patients for three days in a row: a preliminary study A high accuracy voltage approximation model based on object-oriented sensitivity matrix estimation (OO-SME model) in electrical impedance tomography Influence of acute water ingestion and prolonged standing on raw bioimpedance and subsequent body fluid and composition estimates Worth the wait? Time course of supine shifts in body water compartments on variables of bioelectrical impedance analysis Validation of non-empirical fat-free mass estimation model for a wrist-worn device Bioimpedance-based authentication of defrosted versus fresh pork at the end of refrigerated shelf life Bioelectrical impedance changes of the trunk are opposite the limbs following acute hydration change Probing deep lung regions using a new 6-electrode tetrapolar impedance method Intravascular, interstitial and intracellular volume changes during short term deep tissue massage of the calf: A case study The Russian bioimpedance database: an update Development of a small footprint device for measuring electrodermal activity in the palm of the hand Identification of contractions from Electrohysterography for prediction of prolonged labor Cardiovascular diseases diagnosis by impedance cardiography Opinion: The future of electrical impedance tomography Characteristics of Rheoencephalography and some associated factors on menopausal women Comprehensive biotechnical system for screening risk-based diagnosis of COVID-19 and post-COVID syndrome Diabetic foot assessment using skin impedance in a custom made sensor-sock Body composition changes in the immediate peri-operative period following total joint arthroplasty Correlation of the DNA concentration of human samples to electrical bioimpedance measurements: a pilot study A portable band-shaped bioimpedance system to monitor the body fat and fasting glucose level