Device-based physical therapies in chronic pruritus: a narrative review.

Chronic pruritus is a highly prevalent disease associated with high psychosocial and economic burdens. In addition to pharmacological treatments, device-based physical therapies also offer antipruritic effects. Phototherapy, laser treatment, electrical neurostimulation technologies, acupuncture, cryotherapy, and cold atmospheric plasma are, in part, still experimental but emerging treatment options that augment our repertoire to treat patients with chronic pruritus. In this narrative review, we provided an overview of these physical modalities and their role in itch management.

The impact of phototherapy on itch intensity and itch-related quality of life amongst different skin diseases, skin phototypes and genders - A prospective study with 102 patients.

BACKGROUND: Phototherapy is a mainstay to treat itchy conditions. However, only little is known about differences in the antipruritic effect of phototherapy amongst different skin conditions, phototypes and genders. METHODS: In this prospective, single-center study, we analyzed the effect of phototherapy on itch intensity and itch-related quality of life amongst these subgroups after a treatment duration of 4 weeks, while on-demand treatment with topical corticosteroids, topical calcineurin inhibitors and/or antihistamines was allowed. RESULTS: Of 102 patients (age 53.0 ± 18.7, 56 females [54.9%]), 72 (78.3%) reported a significant reduction of itch intensity by Δ -2.76 on a 0-10 Numerical Rating Scale (NRS), p = <.001, 95% CI [2.2; 3.3] paralleled by a significant improvement of itch-related quality of life as measured by the German version of the ItchyQoL by Δ 7.3, p = <.001, 95% CI [4.4; 11.6]. The best improvement of itch intensity and itch-related QoL was reported by patients with pruritus on non-diseased skin (ΔNRS -3.5; Δ 9.7 Ger-ItchyQoL points), followed by patients with atopic dermatitis and psoriasis. We found no statistical differences in the response to phototherapy amongst Fitzpatrick phototypes I-VI. Women had higher itch intensities at baseline but itch-related quality of life impairment at baseline and phototherapy treatment response did not significantly differ between genders. CONCLUSION: Phototherapy appears to induce a meaningful itch reduction in various itchy skin conditions, all phototypes and both genders within 4 weeks that directly translates into improvement of itch-related quality of life.

Conventional and Novel Treatment Strategies for Porokeratoses: A Narrative Review.

Porokeratoses are a heterogenous group of autoinflammatory keratinization disorders all characterized by the presence of a cornoid lamella. In addition to gene mutations affecting the mevalonate pathway, environmental factors such as UV radiation, immunosuppression, trauma, and infection are also thought to contribute to porokeratoses. To date, there are no management guidelines or levels of evidence for commonly used pharmacologic and non-pharmacologic treatment options for porokeratoses. Conventional treatment strategies encompass topical and systemic drugs (e.g., salicylic acid, topical glucocorticoids, and retinoids), phototherapy, laser, and surgical interventions. Better insights into the pathogenesis of porokeratoses have paved the way for the development of novel therapeutic approaches, such as topical statins or the use of monoclonal antibodies. This narrative review aims to summarize both conventional and novel treatment options, including their level of evidence, advantages, and disadvantages.

Pruritus in cutaneous graft-versus-host disease: A systematic review.

Pruritus is a common symptom of cutaneous graft-versus-host disease (GVHD) following haematopoietic stem cell transplantation (HSCT). However, little is known about its prevalence, pathophysiology, perceptual characteristics, impact on quality of life and response to antipruritic therapies. The aim of this review was to determine the current knowledge on pruritus in cutaneous GVHD. The review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analyses statement. Of the 338 studies screened, 13 were included. The prevalence of pruritus in cutaneous GVHD was reported in three studies, ranging from 37.0% to 63.8%. Only four trials used pruritus assessment tools. There was little or no information on the intensity of pruritus, its qualitative perception, the location of pruritus and the impact of pruritus on quality of life. Antipruritic treatments for GVHD-associated pruritus were mentioned in five studies (38.5%), including topical ointments (steroids, tacrolimus and calcipotriene), broadband UVB, systemic antihistamines and oral ursodeoxycholic acid. In conclusion, pruritus in cutaneous GVHD appears to be common, but very little is known about the pathophysiology, impact on quality of life and effective treatment options. Basic research and controlled clinical trials are warranted to improve knowledge and management of this important issue.

Itch reduction using immersive virtual reality-An experimental pilot study.

In a previous proof-of-concept study we have demonstrated that visual exposure to specific colors results in pruritic or antipruritic effects. To determine the effect of "antipruritic" colors when using immersive virtual reality (VR) and to assess whether psychometric values correlate with the response to the color exposure. In this cross-sectional interventional single-center study, itch patients were exposed to their subjective "antipruritic color" (defined by the Manchester Color Wheel) in a virtual monochromatic room for 10 min using a head-mounted display. Itch intensity rating (0-10 numerical rating scale [NRS]) was repeated at 1-min intervals. Additionally, dermatology life quality index, itch-related quality of life and the Hospital Anxiety and Depression Scale questionnaires were completed. Twenty-two patients (mean age 51.9 ± 23 years, 13 females) participated in the study. Following color exposure for 10 min itch intensity was significantly reduced compared to baseline (exact Wilcoxon signed-rank test, mdn-NRS 4.5 vs 3.0; z = -3.025, p = 0.001), confirmed by the area under the curve (z = -3.118; p = 0.001). No significant correlation between itch reduction and questionnaire scores was found (Spearman's Rho for all questionnaires). Visual exposure to the "antipruritic color" using immersive VR resulted in a significant decrease in itch intensity. This aligns with previous findings on the influence of colors on itch perception. The response of the intervention appeared independent of psychometric values. Thus, color exposure using immersive VR is a promising, low-cost, rapidly-acting, easily-applicable, non-pharmacological experimental antipruritic method.

Proposition of a severity scale for lichen sclerosus: The "Clinical Lichen Sclerosus Score".

Vulvar lichen sclerosus (VLS) is a chronic inflammatory skin disease of the anogenitalarea leading to itch, burning, sexual dysfunction and impaired quality of life. An unmet need in the context of LS is a practical, easily assessable grading scale to classify disease severity and to allow intra- and interindividual comparisons. The objectives of this study were i) to assess the prevalence and severity of 23 items proposed by a recent Delphi consensus group in patients with adult VLS. ii) to develop a clinical severity scale and, iii) to test the interrater reliability of this novel severity scale. A retrospective assessment of the prevalence and severity of 23 items in 143 patients was performed by using patient records and photo documentation to develop a novel clinical severity scale (i.e. the "Clinical Lichen Sclerosus Score" = CLISSCO) for VLS. Thereafter, the CLISSCO was validated by 16 raters. We found that the items proposed by the consensus group vary markedly in frequency and severity. Following selection of the most relevant items, the CLISSCO was developed consisting of 3 "Symptoms", 3 "Signs" and 6 "Architectural changes" rated on a 0-4 point Likert-scale. The intraclass correlation coefficient was excellent for each item, the applicability of the CLISSCO considered user-friendly by the raters. We conclude that the CLISSCO proved to be a user-friendly, reliable tool to assess disease severity in VLS. However, further studies are needed to validate its applicability and value in daily practice and clinical research.

Mucosal side effects in patients treated with topical imiquimod-A scoping review of the literature.

Imiquimod 5% is approved for topical treatment of actinic keratosis (AKs), superficial basal cell carcinoma and condylomata acuminata, the 3.75% formulation for the treatment of AKs and genital warts. Imiquimod has also been used off-label in various other skin conditions (eg, Bowen's disease, lentigo maligna, vulvar intraepithelial neoplasia). As a toll-like receptor 7/8 (TLR7/8) agonist imiquimod induces a local inflammatory response by increased production of cytokines, co-stimulatory molecules, activation of Nk-cells and antigen-specific T-cells. In addition to imiquimod-associated adverse effects at non-application sites such as fever, vertigo or myalgia there have been anecdotal reports of distant inflammatory mucosal reactions-a side effect not declared in the medicinal product information. In this scoping review we collected a total of seven cases of patients with lesions of the oral mucosa and lips and summarized pathophysiological hypotheses to explain this type of side effect. The review is complemented with an illustrated report of a 87-year-old female patient of ours suffering from chronic lymphocytic leukemia (CLL) who developed severe oral mucosal and labial reactions following application of imiquimod 3.75% for treatment of AKs. She denied accidental transfer of imiquimod and was tested negative for herpes simplex virus (PCR) and bacteria (culture) from lesional swabs.

Differences in phototherapy among skin diseases and genders in real-life conditions-A retrospective analysis of the cumulative doses, numbers of sessions, side effects and costs in 561 patients.

BACKGROUND: Phototherapy has been a mainstay therapy for dermatological diseases since more than a century. Although phototherapy is still extensively used and some recommendations exist, only scarce data are available addressing disease-specific differences in cumulative doses, treatment durations and costs. Knowledge of such differences could help to avoid over-/undertreatment, predict treatment duration and costs. Therefore, we sought to determine differences in cumulative doses, numbers of sessions, side effects and costs among different skin diseases and genders in real-life conditions. METHODS: In this single-centre, retrospective study, patients treated with phototherapy between March 2014 and April 2019 were classified into seven diagnostic groups and analysed according to the study goals. RESULTS: Out of 561 patients (age 53.9 ± 20.3 yrs; 52.9% females), 83.7% percent were treated with cabin NB-UVB (mean cumulative dose 17.79 ± 17.11 J/cm2 ). Patients with vitiligo and psoriasis were treated with significantly higher cumulative NB-UVB doses (cabin, local) in comparison with the five other diagnostic groups as were males in comparison with females. Consequently, significantly higher UV-related costs resulted in patients with vitiligo, psoriasis and males. Patients with atopic dermatitis and pruritus were treated with significantly higher cumulative UVA1 doses compared to patients with non-atopic eczema. The complication rate (pooled from all UV modalities) in our population was 3.8% (erythema 3.4%, aggravated itch 0.4% and worsening of symptoms 0.2%). CONCLUSIONS: Our results demonstrate that cumulative doses and phototherapy-related costs vary strongly among skin diseases-a fact not adequately considered in recommendations. A more disease-specific stratification of phototherapy could not only help to optimize outcomes, but also to facilitate comparability of clinical trials using phototherapy.

Antihistamines in Psoriasis.

Psoriasis is polygenic, interleukin (IL)-17 and IL-23 driven chronic relapsing inflammatory multisystem disease caused by a complex interplay of endogenous and environmental factors. The most common and distressing symptom in psoriasis is itch, adding significantly to the burden of disease. Although histamine has historically not been considered a key itch mediator in psoriasis, there is some evidence from the literature that antihistamines may be effective to reduce itch in psoriasis. This review focuses on the role of antihistamines in the management of itch in psoriasis. The literature search included peer-reviewed articles published in English language (clinical trials or scientific reviews). Studies were identified by searching electronic databases (MEDLINE and PubMed) until January 2021 and by reference lists of respective articles. J Drugs Dermatol. 2021;20(8):844-847. doi:10.36849/JDD.5966.

Molecular patterns in salivary duct carcinoma identify prognostic subgroups.

Salivary duct carcinoma (SDCa) is a rare cancer with high rate of metastases and poor survival despite aggressive multimodality treatment. This study analyzes the genetic changes in SDCa, their impact on cancer pathways, and evaluates whether molecular patterns can identify subgroups with distinct clinical characteristics and outcome. Clinicopathologic details and tissue samples from 66 patients (48 males, 18 females) treated between 1995 and 2018 were obtained from multiple institutions. Androgen receptor (AR) was assessed by immunohistochemistry, and the Illumina TruSight 170 gene panel was used for DNA sequencing. Male gender, lympho-vascular invasion, lymph node metastasis, and smoking were significant predictors of disease-free survival. AR was present in 79%. Frequently encountered alterations were mutations in TP53 (51%), PIK3CA (32%) and HRAS (22%), as well as amplifications of CDK4/6 (22%), ERBB2 (21%), MYC (16%), and deletions of CDKN2A (13%). TP53 mutation and MYC amplifications were associated with decreased disease-free survival. Analysis of cancer pathways revealed that the PI3K pathway was most commonly affected. Alterations in the cell cycle pathway were associated with impaired disease-free survival (HR 2.6, P = 0.038). Three subgroups based on AR and ERBB2 status were identified, which featured distinct molecular patterns and outcome. Among AR positive SDCa, HRAS mutations were restricted to AR positive tumors without ERBB2 amplification and HRAS mutations featured high co-occurrence with PIK3CA alterations, which seems specific to SDCa. AR negative SDCa were associated with poor disease-free survival in multivariate analysis (HR 4.5, P = 0.010) and none of these tumors exhibited ERBB2 amplification or HRAS mutations. AR and ERBB2 status in SDCa thus classifies tumors with distinct molecular profiles relevant to future targeted therapy. Furthermore, clinical factors such as smoking and molecular features such as MYC amplification may serve as markers of poor prognosis of SDCa.

Contagious itch and disgust during a lecture on ectoparasitic infestations: Two co-activated complementary parasite defense systems?

(Audio-)visual itch transmission is referred to as "contagious itch" (CI) and has been linked to an evolutionarily ingrained ectoparasite defense system. Disgust is considered to be part of the behavioral immune system aimed to prevent the spreading of pathogens. Although they probably serve a similar purpose, the relationship between CI and disgust is unknown. We investigated their co-prevalence, correlation, and differences between the sexes and between skin-diseased and skin-healthy individuals. Medical students attending a lecture on ectoparasitic infestation indicated their change in itch and disgust compared to baseline on a 0 to 10 numerical rating scale (NRS) and specified which ectoparasitic infestation induced CI and disgust the most. Out of 132 participants, 87.9% reported CI, 84.1% disgust. The maximum intensity of CI was 3.68 ± 2.08 NRS (P < .0001), of disgust 3.80 ± 2.68 NRS (P < .0001), respectively. The CI and disgust correlated positively (rho 0.272; P = .002), but we also found that specific ectoparasitic infestations triggered rather itch than disgust and vice versa. Our results indicate that CI and disgust are coincident phenomena of distinct defense systems: CI is aimed to scrape off ectoparasites, disgust to prevent ingestion of pathogens. Furthermore, our data point to differences in CI and disgust between the sexes and skin-healthy vs skin-diseased participants.

Internet and social media use in dermatology patients: Search behavior and impact on patient-physician relationship.

The traditional patient-physician relationship is being changed by the patients' searches for medical information on the Internet and in social media (SM). Freely available medical information online bears enormous potential but also holds dangers. In this cross-sectional, questionnaire-based study, the patients' motivation, preferences and unmet needs when searching for medical information online and the impact on the patient-physician relationship were assessed using Spearman's correlation coefficients, χ2 -tests and paired t-tests. Among 460 participants, 82.4% had already used the Internet/SM to gain medical information, but in only 9.4% their dermatologists had raised this topic. Online search for medical information was associated with female gender (P = .048), a higher skin-related burden (P = .020), higher level of education (P = .072), higher income (P = .019), anxiety (P = .004), and adnexal skin diseases (P = .043). For 16.1% of patients, "the Internet/SM" was their most important source of medical information; 81.4% deemed the impact of their online searches on their patient-physician relationship as neutral, 16.0% as positive, 2.6% as negative. The patients' top three unmet needs were "Online consultations", "Professional content on YouTube" and "Chat opportunities". Online search for medical information is a very important topic for most dermatology patients but it may not be adequately addressed by dermatologists. Our results indicate that from the patients`perspective such online searches do not have a significant impact on patient-physician relationship.

Pruritic and antipruritic colors: An exploratory pilot study.

Itch is the commonest skin-related symptom and can be influenced by visual cues as exemplified by the phenomenon of "contagious itch." Colors are visual cues able to modify somatosensory inputs. We explored the relationship of colors and itch and the impact of color viewing on itch intensity. In this cross-sectional study, patients suffering from itch with a mean intensity of ≥2 on a Numerical Rating Scale during the last 7 days were evaluated. The study consisted of a questionnaire-based part using The Manchester Color Wheel and the ItchyQoL, followed by an interventional part. All 72 itch patients were able to match their itchy sensation with a color: In 68 patients (94.4%) this "pruritic" basic color was red. Likewise, all patients were able to define a subjective "antipruritic" color: The leading basic color choice was blue (31/72, 43.0%) followed by green (21/72, 29.1%), yellow (7/72,9.7%) and others. The impairment of the itch-related quality of life (as measured by the ItchyQoL) correlated with the brightness and saturation of the pruritic and antipruritic colors. Ten patients were visually exposed to their subjective antipruritic and pruritic color during 10 minutes resulting in a significant decrease and increase of itch intensity compared to baseline (5.1 ± 1.52 vs. 2.8 ± 1.47 [0-10 Numerical Rating Scale, NRS], p=0.0004 and 4.9 ± 1.66 vs. 6.8± 2.09 NRS, p=0.0009). These results indicate that itch can be modified by color viewing and colors matter when treating itch patients. However, further investigations are required to elucidate the therapeutic potential of colors in itch patients.

Global Trends in YouTube and Google Search Activity for Psoriasis and Atopic Eczema: Detecting Geographic Hot Spots, Blind Spots and Treatment Strategies.

To date, the geographical distribution and global trends of search activities on psoriasis and atopic eczema on Google and YouTube are widely unknown. The aim of this study was to identify geographic and temporal trends in YouTube and Google search activities for psoriasis and atopic eczema. We used specific filter settings on Google Trends to indicate the global search activity for ("Psoriasis") and ("Atopic Eczema") on Google and YouTube between January 1st , 2008 and August 7th , 2019. The four resulting data sets were analyzed and compared with respect to geographic distribution and temporal trends. Apart from a few "blind spots" (eg, Chad, Uzbekistan) the term "Psoriasis" was queried geographically fairly evenly distributed. The opposite was true for "Atopic Eczema", which was predominantly queried from a few "hot spots" (eg, United States, Commonwealth of Nations and Sweden). Since 2008, the search activity on YouTube for "Psoriasis" has tripled, while that for "Atopic Eczema" has decreased. On Google, by contrast, search activity has risen for both "Psoriasis" and "Atopic Eczema." Google Trends can be a useful tool to track people's/patients' interests and search search behavior over time, enabling, for instance, regionally tailored information and prevention campaigns.

Pain reduction by dehydrated human amnion/chorion membrane allograft in nondiabetic leg ulcers might be an early indicator of good response: A case series.

Dehydrated human amnion/chorion membrane allograft (dHACM) derived from placenta is increasingly used for skin and soft tissue repair in several medical specialties. Promising effects of dHACM were also reported in chronic venous and diabetic leg ulcers. However, dHACM is cost-intensive and its effect on chronic leg ulcers of other etiologies and pain reduction is unknown. Clinical predictors of a favorable response to dHACM during the early treatment period could help to limit unnecessary costs. In our case series with six patients suffering from chronic lower leg ulcers of various etiology, the effect of dHACM once per week on reduction of pain and wound size during a 5-week period was examined. dHACM resulted in effective pain reduction and improved wound healing in three patients with chronic leg ulcers due to calciphylaxis, chronic venous disease and reactive angioendotheliomatosis. Pain reduction after 1 to 2 applications of dHACM predicted a favorable healing response. Hence, our observation indicates that assessment of pain 3 weeks after initiation of dHACM may be a clinical predictor to justify dis-/continuation of dHACM and thereby may help to limit costs.

When life is an itch: What harms, helps, and heals from the patients' perspective? Differences and similarities among skin diseases.

Itch is the commonest skin-related symptom, associated with a high psychosocial and economic burden. While the main focus of itch research lies on a few chronic skin diseases, only little is known about the perception of itch, itch-aggravating/-relieving factors and treatment preferences in patients with acute and chronic itch of various etiology. In this cross-sectional study, we assessed these aspects in 126 patients (mean age 61.7 ± 18.4 years, 67 females, median itch duration 3.9 years) using a 78-item questionnaire. The diseases were categorized into 11 diagnostic groups for descriptive analysis; the three most frequent groups ("atopic dermatitis," "nonatopic eczema," "inflammatory dermatoses") were statistically compared. Itch was most often perceived as localized 42.9%, burning (40.5%), and worrying (39.7%) with worsening in the evening (49.2%), due to warmth (42.1%) and sweating (26.2%). While itch perception, itch-aggravating factors and treatment preferences differed broadly among patients, the itch-relieving personal strategies were more uniform ("scratching by hand 70.6%, applying topicals 57.9%). Also, 69.8% of patients suffered from itch-related sleep disturbance, consequently affecting their relatives in 30.0%. Subgroup comparisons revealed significant differences regarding itch-aggravating factors (P = .0012) and itch duration (P = .0082). Patients rated the antipruritic effectiveness of phototherapy, "complementary and alternative medicine" and "other tablets" as high, but oral antihistamines, "cortisone tablets" and any topical as only moderately efficacious. The preferred administration of an ideal itch treatment was "creams/ointments" (51.6%) or "tablets" (35.7%), only few patients preferred "injections" or "patches." Consideration of such differences and similarities in itch characteristics and treatment preferences could help to better tailor treatment in itch patients.

Pitfall prayer marks: Recognition and appropriate treatment: A case report and review of literature.

Prayer marks are asymptomatic callosities resulting from repeated, extended pressure, and friction exerted on bony prominences when praying on hard ground. A 41-year-old woman with ulcerative colitis treated with infliximab was referred to our clinic due to skin changes on her feet that were suspected to be drug eruptions. The patient presented several asymptomatic, hyperpigmented, and hyperkeratotic plaques over the lateral malleoli suggesting that the lesions had a mechanical cause. Further exploration revealed that the patient, a practicing Muslim, prays in a sitting position called "Julus" several times a day. After color marking, the lesions over the lateral feet left a precise imprint on the underlay when the patient was asked to imitate the praying posture-thus proving the origin of the skin lesions. We searched the database on July 31, 2019 using the terms «prayer marks¼ OR «prayer nodules¼ OR "prayer callosities." Only electronically available publications were reviewed. Recognition of prayer marks is important to avoid misdiagnosis, performance of unnecessary diagnostic procedures, and to enhance the intercultural competence of clinicians who practice in multicultural societies.

Levocetirizine for the treatment of itch in psoriasis patients: An open-label pilot study in a real-world setting.

Itch is the most bothersome symptom in psoriasis, often leading to impaired quality of life. Treatment of psoriasis-induced itch is frequently unsatisfactory as the various therapies employed have a delayed onset of effect. Histamine-1 receptor (H1) antihistamines are not recommended in treatment guidelines as histamine is not considered a key mediator in psoriasis. However, patients using H1 antihistamines frequently report benefits in questionnaire-based studies. To address these contradictions, we examined the short-term effects of levocetirizine, a nonsedating H1 antihistamine, on psoriasis-related itch and itch-related quality of life. In this pilot study, patients with psoriasis-related itch received levocetirizine 5-10 mg daily as a concomitant treatment for 5 days. Change of itch intensity as measured by hourly itch ratings and the change of itch-related quality of life were measured at different time points. A total of 29 of 30 patients (96%) reported a decline in itch within 5 days. Mean itch reduction was 23% after Day 1 (p = .005), 40% after Day 3 (p < .001), and 41% after Day 5 (p < .001). Furthermore, itch-related quality of life also significantly improved after 5 days (p < .001). Only 2 of 30 patients (6.7%) reported mild sleepiness. Levocetirizine 5-10 mg daily as an add-on therapy seems to be an effective treatment to improve itch and itch-related quality of life within only a few days.

Review of biologics in allergic contact dermatitis.

The resistant and recalcitrant nature of severe allergic contact dermatitis (ACD) makes its management challenging. With advances in the understanding of the cellular and molecular pathogenesis of ACD, newer therapeutic targets are becoming apparent. In particular, the use of biologics has gained momentum, given the specificity of their action. This article aims to review the presently available data on the use of biologics in ACD. English-language-based literature available on the use of biological therapy was thoroughly probed in the following databases as on October 14, 2019: PubMed, Google Scholar, The Cochrane library, Embase, Scopus, and EBSCO. The following keywords were used: "contact dermatitis", "allergens", "delayed-type hypersensitivity reaction", "biologics", "biological therapy", "monoclonal antibodies", "patch testing", "TNF-α inhibitors", "infliximab", "adalimumab", "etanercept", "dupilumab", "omalizumab", "secukinumab", "ustekinumab", "rituximab".

Fiction, Falsehoods, and Few Facts: Cross-Sectional Study on the Content-Related Quality of Atopic Eczema-Related Videos on YouTube.

BACKGROUND: In recent years, YouTube has become a recognized source of medical information for health care consumers. Although YouTube has advantages in this context, there are potential dangers as videos may contain nonscientific, misleading, or even harmful information. OBJECTIVE: As little is known about YouTube as a source of information on atopic dermatitis (AD), we investigated the content-related quality of AD videos and their perception among YouTube users. METHODS: The quality of the 100 most viewed AD videos was assessed by using the Global Quality Scale (GQS) and the DISCERN instrument. Videos were classified as "useful," "misleading," and "potentially harmful," and the correlations of viewers' ratings (likes) with the GQS and DISCERN scores were assessed. RESULTS: Among the 100 videos, 68.0% (68/100) and 62.0% (62/100) were of poor and very poor scientific quality, respectively. Additionally, 32.0% (32/100) of the videos were classified as useful, 48.0% (48/100) were classified as misleading, and 34.0% (34/100) were classified as potentially harmful. Viewers' ratings did not correlate with the GQS and DISCERN scores. Overall, 50.0% (50/100) of the videos were posted by private individuals and promoters of complementary/alternative treatments, 42.0% (42/100) by therapeutical advertisers, and only 8.0% (8/100) by nonprofit organizations/universities. CONCLUSIONS: Our study demonstrated that two-thirds of the videos analyzed were below acceptable medical quality standards and that many videos were disseminating misleading or even dangerous content. Subjective and anecdotal content was overrepresented, and viewers did not appear to be able to distinguish between high- and low-quality videos. Health promotion strategies by professional medical organizations are needed to improve their presence and visibility on YouTube.