Topical Therapies

Introduction

Topical management for atopic dermatitis (AD) includes specific guidance on bathing, topical antiinflammatory medications, and antimicrobial approaches. This chapter summarizes the evidence behind and provides recommendations for optimal bathing practices, including frequency, duration, use of cleansers, and additives, and discusses the role of dilute bleach baths. The role of topical antiinflammatory medications is also reviewed, including topical corticosteroid utilization, and gives guidance on how to optimize acute flare management. Second-line therapies, including topical calcineurin inhibitors and phosphodiesterase-4 inhibitors, are similarly discussed, and recommendations are made for the role of these medications in AD. Lastly, the history behind the use of topical antimicrobial treatments and the importance of limiting their utilization is discussed. In sum, this chapter aims to provide an overview of the topical approach to AD, providing recommendations to optimize maintenance and flare-free intervals as well as guidance on the management of acute flares and refractory situations.

Bathing

Bathing represents a crucial component in the management of AD for epithelial hydration. It is also a salient factor of skin hygiene and can remove allergens, irritants, scale, and crust ( ). However, due to accompanying evaporation, overbathing or improper bathing can also lead to epithelial dryness and decreased epithelial barrier function driven by transepidermal water loss and the drying of the stratum corneum ( ). In practice, patients are often subject to conflicting recommendations from providers. Here, the aim is to present evidence supporting frequency and duration of bathing, the use of specific cleansers and/or soaps, dilute bleach baths, bath additives, and other less-studied bathing practices that may be observed in clinical practice.

Frequency of bathing

It is essential to note that all bathing recommendations discussed here are accompanied by the additional directive for application of a moisturizer or emollient ideally within 3 minutes of bathing. The time window is ideal at sealing in hydration and preventing the negative aspects of evaporation. Baths should be taken in lukewarm to warm water that is comfortable to the patient’s skin; excessively hot or cold water temperatures should be avoided. Further, no literature to date directly compares baths versus showers in AD patients, and as such, all recommendations in this chapter should be applied to both bathing methods.

The American management of AD guidelines recommends daily bathing, whereas the European guidelines do not explicitly comment on frequency ( ). Regardless, patients often receive conflicting recommendations. Historically, primary care physicians tend to recommend infrequent bathing; conversely, allergists, immunologists, and dermatologists have recommended frequent bathing ( ). These conflicting messages have been driven by the fact that some physicians have viewed bathing as drying to the skin, and specialists have viewed it as hydrating. Multiple survey studies have confirmed this trend ( ). Up to 75% of patients/families have reported confusion in how frequently to bathe, and 45.6% have reported receiving conflicting advice ( ). The primary benefit of bathing most likely stems from its hydrating qualities rather than its cleansing properties ( ).

Type of bathing and duration

Similar to the frequency of bathing, recommendations for duration historically lack consensus. The American Academy of Dermatology (US) guidelines recommend 5- to 10-minute baths, followed by the immediate application of emollients ( ). European guidelines recommend shorter (5-minute) baths, with the addition of bath oils in the final 2 minutes, followed by patting dry, and the immediate application of emollients ( ). Retrospective cohort studies have not shown a statistical significance between short bathing (<5 minutes) versus medium length bathing (5–10 minutes); extended baths (10–30 minutes) are associated with more severe AD ( ). This association of severity with longer duration of bathing may be confounding as those with more severe AD may bathe longer ( ). Those with severe AD and those with frequent infections are often recommended to take “soak and smear” baths, which consist of bathing for approximately 10 minutes, followed by the immediate application of antiinflammatory medications ( ). The US guidelines explicitly recommend such baths for patients with frequent exacerbations ( ).

Cleansers, soaps, and bathing practices

An essential component of bathing is the appropriate use of cleansers and soaps. The epidermis has a mildly acidic pH ranging between 4 and 5.5 ( ). This acid mantle is crucial for skin’s innate antimicrobial action and maintenance of the skin barrier ( ). Most soaps are alkaline due to the process of saponification. Exposure of the skin to this alkalinity can disrupt the epithelium’s acid mantle and be directly damaging to the stratum corneum leading to increased water loss and causing rigidity of the lipid components ( ). Soaps also remove physiologically normal oils and contain detergents and surfactants that can damage the epithelium leading to irritation and dry skin ( ).

Patients are presented with an abundance of options when choosing bathing products, including soaps, cleansers, and synthetic detergents (syndets). Soaps are made of long-chain fatty acid alkali salts created from the process of saponification; cleansers are mixtures of water and some form of active compound, including soaps, emulsifiers, surfactants, and detergents ( ). Syndets are nonsoap synthetic surfactants. One study examined the pH of all commercially available soaps and cleansers and found that all bars of soap had a pH between 9.9 and 10.7 except for syndet bars, which had a pH of 7 ( ). In the same study, most liquid cleansers were found to be less alkaline, but many still had a pH between 7.5 and 9.6; again, liquid syndets had a pH of 7 ( ). Based on the harmful effects of soaps and alkalinity, patients with AD are usually advised to use nonsoap hypoallergenic cleansers containing a neutral or mildly acidic pH ( ). Guidelines from Korea, Italy, and the United States directly recommend the use of syndets ( ). Notably, one study found that for patients with AD, the daily use of mildly acidic syndets significantly reduced clinical severity and symptomology in patients compliant with the regimen compared to those who were not ( ). Further, some data have shown that there may be no significant difference in eczematous symptoms when the use of soap is compared with bathing with water alone ( ). Thus daily cleanser use is not needed in AD patients, especially prepubertal children, as their potentially sensitive skin may be at high risk of experiencing irritating effects, and the sebum content of their skin is relatively lower (compared to adolescents and/or adults). In sum, the usage of neutral to mildly acidic cleansers should be recommended to patients, and they should also be counseled on the harmful effects of alkalinity.

Patients should also be directed to avoid damaging the epithelial barrier when using cleansers and take active steps to minimize friction when applying or removing soaps. They should be counseled to gently apply cleansers with the hands or soft microfiber cloths only, and to avoid the use of rougher texture wash cloths, loofahs, firm sponges, and/or scrubbing, as there is a risk of direct physical irritation. Cleansers should be quickly and gently rinsed off.

One unique aspect of bathing to be stressed with patients is the appropriate application of emollients. In 2009, a crossover study compared bathing without any application of emollients, bathing with immediate application, bathing with delayed 30-minute application, and emollient application without bathing effects on epithelial hydration ( ). This study found that patients who did not apply an emollient postbathing had decreased epithelial hydration in comparison to the emollient treatment arms ( ). Thus patients should be counseled that bathing without any application of an emollient may have directly negative impacts on epithelial hydration and be instructed to always use a postbath emollient.