Howard Maibach

• University of California, San Francisco

Contact urticaria (CoU) is an immediate contact reaction occurring within minutes to an hour after exposure to specific proteins or chemicals. CoU is categorized into non-immunologic (NI-CoU) and immunologic (I-CoU) types, with I-CoU potentially leading to anaphylaxis. Both forms of CoU can be associated with protein contact dermatitis and the cont...

Exogenous allergens, found in cosmetic products, jewelry items, antiseptics and antibacterials, plants, and solvents, can cause clinical allergic contact dermatitis (ACD). To help identify and discern which allergen is causing ACD, clinicians use patch tests, but they can yield false-negative results at times. Examining potential reasoning for fals...

Though recent studies have hinted at associations between allergic contact dermatitis (ACD) and infectious diseases, extensive cohort analyses on the direct correlations between ACD and increased susceptibility to these infections remain limited. After analyzing the “All of Us” database, which includes a diverse cohort of 287,011 participants, the...

Background: Allergic contact dermatitis is frequently caused by metals, including multiple metals simultaneously. Objectives: To assess characteristics and associations of positive and clinically relevant patch test (PT) reactions with solitary and concurrent metal sensitization. Methods: A retrospective analysis of PT results for nickel, cobalt, a...

Dear Editor, Rosacea is characterized by a complex genetic, environmental and vascular aetiology and predominantly manifests as facial erythema, oedema and pronounced vascular patterns. Although recent studies have hinted at associations with psychiatric conditions, extensive cohort analyses remain limited. This study sought to bridge this gap usin...

Topical delivery systems (TDSs) enable the direct transport of analgesics into areas of localized pain and thus minimize the side effects of administration routes that rely on systemic drug distribution. For musculoskeletal pain, clinicians frequently prescribe topical products containing lidocaine or diclofenac. This study assessed whether drug de...

It is common for people to be exposed to multiple topical products daily, either through cosmetics, personal care or drug formulations. This increases the possibility of contact dermatitis and poses a major challenge for treatment as well as the design and regulation of safe and effective topical products. Here, we define the scope of the problem o...

Androgenetic alopecia is a widespread condition that is the most common type of hair loss affecting approximately 58% and 40% of men and women by the age of 50, respectively. Patients have been known to experience severe distress due to androgenetic alopecia, including anxiety, low self-esteem, and depression. The objective of this study was to con...

Background: Vitiligo is a multifaceted autoimmune depigmenting disorder affecting around 0.5 to 2.0% of individuals globally. Standardizing diagnosis and therapy tracking can be arduous, as numerous clinical evaluation methods are subject to interobserver variability and may not be validated. Therefore, there is a need for diagnostic tools that are...

Introduction Percutaneous absorption is the deliverance of topically encountered molecules into the systemic circulation. This process can be harnessed therapeutically when prescribing topical medications, but is also the culprit of many toxicities. Many factors influence percutaneous absorption, an important yet understudied one being blood flow t...

For more than five decades, pharmaceutical manufacturers have been relying heavily on batch manufacturing that is a sequential, multistep, laborious, and time-consuming process. However, late advances in manufacturing technologies have prompted manufacturers to consider continuous manufacturing (CM) is a feasible manufacturing process that encompas...

Abstract Hidradenitis suppurativa (HS) is a chronic, profoundly incapacitating disease predominantly affecting the apocrine gland-rich areas of the human body. Although it affects 0.05% to 4% of the general population, there exists a significant racial disparity, with people of color, particularly Black individuals, experiencing a notably higher pr...

Microneedles (MNs) are needles with a tip diameter ranging from 10 to 100 um and a length ranging up to 1 mm. The first patent for drug delivery device for percutaneous administration filed by Alza corporation dates back to 1976 (Gerstel and Place, 1976), and in between 1989 and 2021 the filed patents for MNs are more than 4500 (Banks et al., 2010)...

Background: Allergic contact dermatitis (ACD) caused by hexavalent chromium (Cr(VI)) is often severe and difficult to treat. The content of Cr(VI) in cement can be reduced by, for example, addition of iron(II) sulfate. Since 2005 the content of Cr(VI) in cement is regulated in the EU Directive 2003/53/EC and must not exceed 2 ppm. Since this regula...

Contact urticaria syndrome includes contact urticaria and protein contact dermatitis. These entities are usually found in an occupational setting, with diverse epidemiologic characteristics. It is believed that these conditions are underreported, underdiagnosed, and/or misdiagnosed. Their clinical presentation includes not only immediate urticaria...

Purpose of Review Vitiligo is an acquired condition resulting from melanocyte disappearance and clinically manifests as explicit white patches. Limited research exists on its distribution patterns, specifically, its predisposition for certain anatomic sites, such as the face and extensor surfaces, and any unique structure and function of these site...

Androgenetic alopecia is a widespread condition that is the most common type of hair loss affecting approximately 58% and 40% of men and women by the age of 50, respectively. Patients have been known to experience severe distress due to androgenetic alopecia, including anxiety, low self-esteem, and depression. The objective of this study was to con...

Dermatological diseases are widespread and have a significant impact on the quality of life of patients; however, access to appropriate care is often limited. Improved early training during medical school represents a potential upstream solution. This scoping review explores dermatology education during medical school, with a focus on identifying t...

Background: Allergic contact dermatitis (ACD) remains a public health issue worldwide, despite regulations intended to minimize sensitization. With up-to-date knowledge about which chemicals continue to have high allergenicity, the government/industry can refocus their efforts to be most effective. Objective: We reviewed updated data showing common...

Objectives: Sexual and gender minority (SGM) patients face health issues relevant to dermatologists, such as allergic contact dermatitis (ACD); however, there is a lack of information surrounding common allergens causing ACD that disproportionally affect SGM patients. Methods: Covidence, Embase, MEDLINE, PubMed, Web of Science, and Google Scholar w...

Percutaneous absorption assays assess the safety of substances that may contact the skin, such as topical medications, skin/hair care products, industrial chemicals, and pesticides. In this chapter, we will discuss the rationale, procedure, accuracy, safety, advantages, and disadvantages of these assays when experimented with in vitro and in vivo,...

Background: Benzophenone (BZP)-3 and BZP-4 are ultraviolet (UV) absorbers used in sunscreens and personal care products (PCPs) and may cause allergic contact dermatitis. Objective: To characterize positive patch test reactions to BZP-3 (10% in petrolatum [pet]) and BZP-4 (2% pet) in a screening allergen series. Methods: Retrospective analysis of pa...

Background: Patch testing is an important diagnostic tool for assessment of allergic contact dermatitis (ACD). Objective: This study documents the North American Contact Dermatitis Group (NACDG) patch testing results from January 1, 2019, to December 31, 2020. Methods: At 13 centers in North America, patients were tested in a standardized manner wi...

Objective: Skin of color patients face important health issues relevant to dermatologists, such as allergic contact dermatitis; however, there is a lack of information surrounding common allergens causing contact dermatitis that disproportionately affect skin of color patients, as well as interpreting patch testing in this population. Methods: Covi...

Importance The common use of isothiazolinones as preservatives is a global cause of allergic contact dermatitis. Differences in allowable concentrations of methylisothiazolinone (MI) exist in Europe, Canada, and the US. Objective To compare the prevalence of positive patch test reactions to the methylchloroisothiazolinone/methylisothiazolinone (MC...

Purpose of Review Pityriasis lichenoides (PL) is a spectrum of dermatological conditions involving polymorphous lesions. Natural history of the condition ranges from acute to chronic. Cases of PL following SARS-CoV-2 infection/vaccination have been reported, but not yet comprehensively reviewed. Hence, the objective of this article is to review and...

The objective of the project was to investigate the plausibility of active pharmaceutical ingredients (APIs) to undergo sublimation from topical application following evaporation of solvent. Topical formulations with different APIs were subjected to a sublimation screening test. The APIs in the selected topical products were found to undergo sublim...

Background: Cobalt is a recognized cause of allergic contact dermatitis (ACD); however, detailed information on patient characteristics, sites, and sources is lacking. Objective: The aim of the study is to assess trends in patch test reactions to cobalt and associated patient characteristics, common sources, and body sites affected. Methods: The st...

Sunscreen application is widespread and incorporated into daily life. Although FDA has approved 16 sunscreen ingredients, recent studies suggest a revaluation of their potential adverse effects. This systematic review assesses sunscreens’ percutaneous absorption, toxicity, and their ingredients concentration in urine and plasma. The search was cond...

Pityrosporum folliculitis (PF) is a fungal acneiform disease of the hair follicles that often presents with pruritic papules and pustules on the upper body and face. This condition is commonly mistaken for acne vulgaris and can be distinguished from bacterial acne by the presence of fungal spores in the follicular lumen. Although studies have been...

Background: Dental personnel are at risk of developing occupational contact dermatitis. Objectives: The aims of the study were to determine prevalence of occupational contact dermatitis in dental personnel referred for patch testing and to characterize relevant allergens and sources. Methods: The study used a retrospective, cross-sectional ana...

Background: Shoe contact allergy can be difficult to diagnose and manage. Objective: The aim of the study was to characterize demographics, clinical characteristics, patch test results, and occupational data for the North American Contact Dermatitis Group patients with shoe contact allergy. Methods: This is a retrospective study of 33,661 pati...

Background: An updated understanding of allergic contact cheilitis is needed. Objectives: To characterize clinical characteristics and allergen relevance in patients with cheilitis referred for patch testing. Methods: Retrospective analysis of 43,772 patients patch tested with the North American Contact Dermatitis Group (NACDG) screening serie...

Polymeric microneedles were prepared with Polyvinyl Pyrrolidone (PVP) K-30 using the mold casting technique. The core microneedles were coated with Eudragit E-100 by dip and spin method. The amount of 5-fluorouracil (FU) loaded in the core microneedles was 604 ± 35.4 µg. The coating thickness was 24.12 ± 1.12 µm. The objective was to deliver the 5-...

Purpose of Review Contact urticaria syndrome includes contact urticaria and protein contact dermatitis. Underreport, underdiagnosis, or misdiagnosis of entities within the contact urticaria syndrome is believed to be common, especially in the occupational setting. This review provides a structured overview of the entities comprised in this syndrome...

Introduction The accumulation of tissue‐advanced glycation end products in skin results from complex and consecutive reactions and can be measured by skin autofluorescence (SAF) reader devices. This overview discusses studies evaluating the utilization of SAF in screening renal and cardiac disease. Materials and methods Literature search was perfo...

Objectives: Sexual and gender minority (SGM) patients face health issues relevant to dermatologists, such as allergic contact dermatitis (ACD); however, there is a lack of information surrounding common allergens causing ACD that disproportionally affect SGM patients. Methods: Covidence, Embase, MEDLINE, PubMed, Web of Science, and Google Schola...

Percutaneous absorption of chemicals is a potential route of topical and systemic toxicity. Skin decontamination interrupts this process by removing contaminants from the skin surface. Decontamination using water-only or soap and water solutions is the current gold standard despite limited efficacy data. A summary of studies evaluating their effica...

With the constant possibility of occupational exposures, chemical warfare, and targeted attacks, increased attention has been given to determining effective and timely dermal decontamination strategies. This chapter and systematic review summarizes experimental studies reporting decontamination with water-based solutions of dermal chemical contamin...

Water-only or soap and water solutions are considered a gold standard for skin decontamination. However, there is lack of conclusive data regarding their efficacy. This study summarizes in vivo animal model data on skin decontamination using water-only and/or soap and water. Covidence, Embase, MEDLINE, PubMed, Web of Science, and Google Scholar wer...

Due to threats posed by chemical warfare agents (CWAs) and accidents with toxic industrial chemicals (TICs), the need for highly effective skin decontamination remains relevant. Reactive Skin Decontamination Lotion (RSDL), composed of Dekon 139 and 2,3-butanedione monoxime, has been shown highly effective against CWAs and TICs. This systematic revi...

Water-only or water and soap are widely recommended as preferred solutions for dermal decontamination. However, limited efficacy data exists. We summarized experimental studies evaluating in vitro efficacy of water-only or soap and water in decontaminating chemical warfare agents (CWAs) or their simulants from human skin models. Embase, Covidence®,...

Water and/or soap and water solutions have historically been used as first-line decontamination strategies for a wide variety of dermal contaminants from workplace exposure, environmental pesticides, and civilian chemical warfare. Although water and/or soap and water solutions are often considered a gold standard of decontamination, many studies ha...

Percutaneous absorption is of importance given its role in topical medicaments, transdermal drug systems, and dermatotoxicology. Many factors influence percutaneous penetration, including anatomical region, although little is currently known regarding this parameter. Hence, the aim of this study was to summarize existing data on regional variation...

At least 20 clinically relevant factors affect percutaneous absorption of drugs and chemicals: relevant physicochemical properties, vehicle/formulation, drug exposure conditions (dose, duration, surface area, exposure frequency), skin appendages (hair follicles, glands) as sub-anatomical pathways, skin application sites (regional variation in penet...

Purpose: The United States will soon be a nation of color; however, much of our knowledge of normal skin disease and treatment thereof is based on white skin. We and others have attempted to elucidate any potential differences and advantages/disadvantages in skin function that have emerged during Homo sapiens evolution post major migration from Eas...

Zinc oxide nanoparticles (ZnO NPs) have small particle sizes (100 nm or less) and large surface areas with numerous highly reactive sites, thus presenting highly reactive catalysts toward environmental toxic chemicals.This in vitro study examined decontamination and detoxification capacities of ZnO NPs to decrease paraoxon (POX) absorption and perm...

Lateral spread, a phenomenon with significance for percutaneous application of drugs or chemicals but often overlooked, is a competitive process to drug or chemical penetration into the stratum corneum and beyond. Its effect may vary depending on factors such as physicochemical properties, formulation, skin surface topography, etc. It may impact cl...

Although skin decontamination has been studied since WWI, there has yet been an optimal protocol for determining in vitro skin decontamination efficacy due to the complexity of percutaneous absorption. Here we explore methods of quantifying decontamination through the parameters of percutaneous absorption in different models: humans, animals, in vi...

Purpose: Despite the wide breadth of research, much disparity exists in transepidermal water loss (TEWL) research data—possibly due to uncontrolled experimental variables. We determined whether such experimental variables significantly impact TEWL studies and cause this disparity. Methods and Materials: An initial literature search regarding TEWL w...

Soap and water are often considered the gold standard for dermal decontamination. However, recent systematic reviews have shown that these methods often result in incomplete decontamination and may even induce contaminant absorption due to the “wash-in” effect. Therefore, it is important to gain insight on other decontamination methods. A literatur...

Background: Allergic contact dermatitis (ACD) remains a public health issue worldwide, despite regulations intended to minimize sensitization. With up-to-date knowledge about which chemicals continue to have high allergenicity, the government/industry can refocus their efforts to be most effective. Objective: We reviewed updated data showing com...

In vitro drug release test has become one of the most important tools for drug development and approval process of semisolid dosage forms. In vitro release test (IVRT) has the ability to reflect the combined effects of several physicochemical characteristics, particle or droplet size, viscosity, microstructure arrangement of the matter and state of...

Background Dermatitis localized to hands (HD), feet (FD), or both hands and feet (HFD) has multiple etiologies including atopic dermatitis (AD), irritant contact dermatitis (ICD), and allergic contact dermatitis (ACD). Little is known about clinical differences between patients with HD, FD and HFD. Objectives To characterize differences of demogra...

Background: Allergic contact dermatitis (ACD) to cobalt is more common in children and adolescents than adults. However, detailed information on sites and sources of cobalt ACD are limited. Objectives: To assess trends in positive and clinically relevant patch test reactions to cobalt in children and associated patient characteristics, common so...

Physicochemical and formulation factors influencing penetration of drugs from topical products into the skin and mechanisms of drug permeation are well investigated and reported in the literature. However, mechanisms of drug absorption during short-term exposure have not been given sufficient importance. In this project, the extent of absorption of...

Background: Transepidermal water loss (TEWL), the total non-eccrine sweat water evaporating from a given area of epidermis over time, is a measurement of skin barrier integrity. Skin diseases (e.g. psoriasis and atopic dermatitis) often result in transient increases in TEWL, so knowledge of "normal" TEWL values may be used to predict disease progr...

Objective Compare the relevance of flow‐through versus static diffusion cells data as relates to bioequivalence. Methods Search was conducted on PubMed and Google Scholar. Keywords utilized: static cells, flow‐through cells, percutaneous permeation, percutaneous absorption, dermal absorption, and types of permeation. Results Fifteen articles were...

Background Alkyl glucosides are nonionic surfactants increasingly used in personal care products (PCPs). Objective To characterize positive patch test reactions to decyl glucoside (5% pet, tested 2009-2018) and lauryl glucoside (3% pet, tested 2017-2018). Methods Retrospective analysis of patients tested by the North American Contact Dermatitis G...

The polymer coated polymeric (PCP) microneedles were fabricated using PVP K30 in the core and ethyl cellulose in the coating. The PCP microneedles do not disintegrate in the tissue upon insertion and rather stays intact and allows diffusion of drugs and analytes across the membrane both inward and outward. In this project the potential use of PCP m...

The concentration of a formulation, defined as the mass of applied chemical per unit of skin surface area, is a key variable of skin absorption. Often only one concentration is available in the literature, hence a general evidence-based theory could allow prediction of how altering the concentration would produce a linear, increased, or decreased r...

Nanotechnology-based formulations have revolutionized the cosmetics industry. Nanoformulations can improve the behavior release of the ingredients and their skin penetration, two important factors in advanced cosmetics technology. Recently, fullerene nanoparticles and their derivatives have gained attention as one of the most developed types of cos...

Background: Lanolin is an important cause of allergic contact dermatitis. Objectives: The aims of this study were to describe the epidemiology of lanolin allergy and to assess trends in patch test reactions to lanolin over time. Methods: This study used a retrospective analysis of patients patch tested with lanolin alcohol 30% or Amerchol L-10...

Background: The process by which drugs leave the bloodstream to enter the skin compartments is important in determining appropriate routes of delivery and developing more efficacious medications. We conducted a general literature review on percutaneous egression mechanisms. Summary: Studies demonstrate that the stratum corneum (SC) is a compartm...

Soap and water are often considered the gold standard for dermal decontamination. However, recent systematic reviews have shown that these methods often result in incomplete decontamination and may even induce contaminant absorption due to the "wash-in" effect. Therefore, it is important to gain insight on other decontamination methods. A literatur...