UNASSIGNED: Frontal fibrosing alopecia (FFA) is a form of lichen planopilaris with an undetermined etiopathogenesis, predominantly affecting women. There is conflicting evidence as to whether contact allergens may play a role in the underlying etiology or progression of FFA.
UNASSIGNED: The aim of this study is to find the most common products that patients search for online, identify contact allergens present in these advertised over-the-counter hair products, and suggest their role in the development or exacerbation of FFA.
UNASSIGNED: We reviewed current research on this topic and then investigated common allergens found in over-the-counter hair products commonly used for hair regrowth.
UNASSIGNED: FFA\'s exact etiopathogenesis remains vastly unknown, however, current literature has reported an association between inflammatory skin conditions and FFA.
UNASSIGNED: The lack of published data on the function of contact allergens in FFA placed restrictions on our study.
UNASSIGNED: A survey-based analysis with a larger cohort is needed to further interpret the relationship between product use and FFA presentation based on contact allergens. More research on possible etiopathogenesis and the relationship between contact dermatitis and FFA may prevent further progression of a patient\'s disease, leading to an improvement in their quality of life.

OBJECTIVE: Nickel (Ni) is the most common contact allergen in the population. We aimed to investigate whether there is a relationship between Ni sensitivity and irritable bowel syndrome (IBS) in our study.
METHODS: This study was conducted in 50 patients with IBS who were followed up between March 2018 and July 2018, and 40 healthy people as a control group in a single center with a dermatology department. European standard contact allergen series Ni preparate and corticosteroid pomace were applied to the back region of the study subjects. The evaluation was performed at 48, 72, and 96 hours according to the scheme proposed by the International Contact Dermatitis Research Group (ICDRG). Those who reacted at 72 hours were considered to have Ni allergy.  Results: The female/male ratio was 24/26 and 18/22 in the patient and control groups, respectively. The mean ages of the patient and control groups were 42.82 (±10.65) and 39.77 (±11.21) years, respectively. Ni sensitivity was present in 40% of the patient group and 17.5% of the control group (p=0.03).
CONCLUSIONS: We believe that the presence of Ni sensitivity is important in the pathogenesis of IBS disease. In our study, Ni sensitivity was found to be quite high in IBS patients compared to the normal population.

Surfactants are long-chain compounds comprising a hydrophobic tail and a hydrophilic head, lending them the ability to act as a “bridge” between oil and water. Their detergent, foaming and other properties prove useful in a number of settings, including home and workplace sanitation, cosmetics (rinse and no-rinse cleansers) and medicine. When used on skin, surfactants reduce the superficial surface tension of proteins and lipids on the stratum corneum. This helps to eliminate skin debris such as sebum, oils and dirt, but also presents a risk of damage to the skin barrier. The irritation potential of surfactants has long been common knowledge, but with the development and deployment of novel compounds, notably to replace first-generation, mostly sodium-lauryl-sulphate-based products, their potential to cause allergic contact dermatitis has come to light. Knowledge about this allergic potential and the associated dermatitises must also become commonplace so that contact allergies are considered in the presence of surfactant exposure.

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This chapter summarises all relevant aspects of patch testing, closely following recommendations outlined in a recent European, and a German S3 guideline on diagnostic patch testing with contact allergens and medicinal products (drugs). Patch testing is indicated in patients suspected of suffering, or having been suffering, from delayed-type hypersensitivity leading to allergic contact dermatitis or other skin and mucosal diseases. Sections of this chapter include detailed indications, reasons for possibly postponing the test, considerations on choosing haptens (contact allergens) to test, various aspects of the application of patch test allergen preparations (storage, dosing) and of testing with individual materials provided by the patients. Special aspects of patch testing in cutaneous adverse drug reactions, children, or occupational contact dermatitis are outlined. Supplemental test methods, notably the repeated open application test, are briefly described. Finally, the final evaluation in terms of assessment of clinical relevance of reactions and patient counselling are outlined.

BACKGROUND: Epidermal T cells play a central role in immune surveillance and in inflammatory skin diseases. Major differences in the epidermal T cell composition are found between adult humans and antigen-inexperienced laboratory mice. Whether this is due to inborn species differences, to different environmental exposures, or a combination of the two is a matter of debate.
OBJECTIVE: To investigate the role of age and exposure to antigens on epidermal T cell subsets in human and mouse skin.
METHODS: We isolated T cells from the epidermis from 19 infants and 26 adults, and determined the frequency of CD4+ and CD8+ αβ T cells and γδ T cells by flow cytometry. In addition, we determined the epidermal T cell composition in antigen-inexperienced and antigen-experienced mice.
RESULTS: We found that humans are born with very few epidermal T cells. The number increases and the composition changes with age. In antigen-inexperienced mice, the epidermal T cell composition is unaffected by age, but it is dramatically affected by antigen exposure.
CONCLUSIONS: Taken together, we show that antigen exposure, as opposed to age, is the major factor determining the composition of epidermal T cells, suggesting that the skin of antigen-experienced mice better reflects the immunological conditions in human skin.

Occupation contact dermatitis (CD) is a common inflammatory skin condition impacting every professional industry in the United States. It is associated with significant personal and professional distress, loss of revenue, and decreased productivity. Occupational CD is further subdivided into irritant CD and allergic CD. Frequently, workers may suffer from a combination of both types. Numerous workplace exposures are implicated, but there are several themes across professions, such as CD related to frequent handwashing and wet work. A detailed occupational history, physical examination, and patch testing can help to make the diagnosis. Treatment includes identification of the substance and avoidance, which often is quite challenging.

We previously demonstrated that based on their potency, contact allergens differently modulate Blimp-1/NLRP12 expression in human keratinocytes, with the extreme allergen 2,4-dinitrochlorobenzene (DNCB) more rapidly upregulating Blimp-1, leading to downregulation of NLRP12, and to the production of interleukin-18 (IL-18). The purpose of this study was to further investigate the effects of DNCB and para-phenylenediamine (PPD) on the expression of the proteins of the inflammasome, namely NLRP3, ASC and caspase 1 by western blot analysis; to define the intracellular localization and co-localization of NLRP3 and NLPR12 by immunoprecipitation and immunohistochemistry; and to define the role of NF-κB in Blimp-1 induction by pharmacological inhibition. The human keratinocyte cell line NCTC2544 was used for all experiments. Dose and time course experiments were performed to evaluate the effect of the selected contact allergens on the parameters investigated. Results indicate, that consistent with previous finding, DNCB more rapidly (3 h) induces NLRP3, ASC protein expression and caspase-1 activation compared to PPD. Immunoprecipitation studies show the recruitment of ASC to the inflammasome following exposure to both allergens, while high level of NLRP12 and less ASC protein were found associated in control cells. By immunohistochemistry, we found increased NLRP3 expression following exposure to contact allergens, and observed a nuclear co-localization of the two proteins, indicating the NLRP12 likely acts preventing the cytosolic localization of NLRP3 and inflammasome assembly. Finally, contact allergen-induced Blimp-1 mRNA and protein expression can be completely blocked by inhibiting NF-κB activation, confirming the central role of NF-κB in contact allergen-induced keratinocyte activation.

Atopic dermatitis (AD) and allergic contact dermatitis (ACD) are common T-cell-mediated inflammatory skin conditions that can share clinical presentations. The variable expression of ACD among patients with AD represents the shades of gray of the multifaceted relationship between the 2 disorders, where increased allergen permeation in compromised epidermal barriers augments antigen presentation and sensitization, with subsequent immune dysregulation. Further studies are needed to define the relationship and immunologic intersection points of these 2 conditions.

The field of contact dermatitis is constantly evolving. Trends in irritant and allergic contact dermatitis are shaped by the introduction of new chemicals, revival of older allergens, industrial practices, and consumer behaviors. This article discusses the most noteworthy trends within the field, organized by allergen category, with particular attention to newer and/or controversial allergens.