Blog Series | Beyond Biocompatibility: Why Human Factors Design Matters for Skin-Worn Devices

8 Part Series Overview | The Importance of Human Factors in Wearable Device Design

A skin-worn product can pass biocompatibility testing, meet its technical specifications, and still struggle in the real world. The materials may be well characterized, the adhesive may perform under controlled conditions, and the software may function exactly as intended. Yet users may still report skin irritation, itching, device falling off, or early product removal.

These outcomes are often treated as separate problems. A materials and design team may see an adhesive issue. A biocompatibility team and clinician may see a contact dermatitis. An ergonomics team may see poor fit. A quality team may classify the event as misuse. In practice, several of these interpretations may be correct at the same time.

That is where human factors becomes useful.

Human factors engineering looks at how people actually interact with a product: what they see, feel, understand, remember, and physically do. It also considers the conditions in which those interactions occur. For skin-worn products, that means sweat, movement, bathing, sleep, heat, humidity, friction, pressure, repeated wear, and the many small workarounds users adopt when a product does not behave as expected.

An skin adhered device may lift after exercise, so the user adds tape. It may itch, but the user continues wearing it to avoid losing data or wasting an expensive sensor. A smartwatch may feel comfortable during the day but create skin irritation when worn overnight. A headset may fit well initially but become warm and irritating after prolonged use. A patch may be applied to skin that is technically intact but still poorly suited for multi-day wear.

None of these events can be understood fully by looking at materials alone.

Why FDA Developed a Human Factors Framework

FDA’s interest in human factors grew from a simple but important observation: medical devices can fail even when the underlying technology works.

A user may misunderstand a display, miss a warning, connect the wrong component, apply a device incorrectly, or fail to recognize when something has gone wrong. These use-related failures can cause serious harm or compromise medical decision making , which makes them a design, risk-management problem and medical safety issue rather than simply a user problem.

The foundational 2016 FDA guidance, Applying Human Factors and Usability Engineering to Medical Devices, provides a structured way to evaluate these risks. It asks manufacturers to consider the intended user, the use environment, the device interface, the tasks required to use the product, the errors that may occur, and the potential harm that could follow.

This creates a common language across engineering, clinical, design, quality, regulatory, and safety teams.

That common language matters because the same event can otherwise be described in very different ways. A skin reaction may be called user error, adhesive failure, poor fit, inadequate labeling, a material response, an environmental effect, or a design defect. Without a shared structure, teams may struggle to identify what actually happened and what should change.

The human factors framework connects the full sequence:

User → task → interface → use error → hazardous situation → potential harm → risk control

For skin-worn products, that sequence might look like this:

A user applies a patch immediately after exercise. The skin is still moist. The adhesive does not seat evenly. One edge lifts. The user reinforces it with tape that is not suitable for prolonged skin wear. Moisture and occlusion increase beneath the device. The skin becomes irritated, and the sensor begins to move. The result is not only dermatitis, but also poor signal quality and early product removal.

Was the problem skin preparation? Adhesive performance? Labeling? Foreseeable user behavior? Product geometry? The answer may be all of the above.

Human factors gives teams a disciplined way to separate those contributions and decide whether the best response is redesign, a protective feature, clearer instructions, additional testing, or better postmarket monitoring.

The 2016 Foundation and the 2026 Update

The 2016 guidance explains how manufacturers should identify use-related hazards, understand intended users and environments, analyze tasks, conduct formative evaluations, implement risk controls, and validate the final interface.

FDA’s 2026 guidance, Content of Human Factors Information in Medical Device Marketing Submissions, builds on that foundation. It introduces a risk-based structure for the human factors information included in regulatory submissions and organizes devices into Human Factors Submission Categories 1, 2, and 3.

The categories depend on questions such as:

• Has the user interface changed?

• Has the intended user population changed?

• Are there new or affected critical tasks?

• Is the interface complex?

• Are existing risk controls still adequate?

• Is new human factors validation needed?

The 2016 document explains how to do the human factors work.

The 2026 document explains how much of that work should be presented to FDA, how it should be organized, and how the manufacturer should justify its conclusions.

Together, they create a more consistent framework for showing that a product can be used safely and effectively by the people for whom it was designed.

Why This is Crucial for Consumer Electronics and General Wellness Products As Well

Consumer electronics and general wellness products are not necessarily subject to the same FDA human factors requirements.

Even so, the underlying lessons are highly relevant.

Consumer wearables now sit on the body for longer periods, collect more sensitive information, deliver more feedback, and increasingly influence decisions about sleep, exercise, stress, recovery and health. As these products become more capable, the cost of poor fit, confusing feedback, skin injury, heat, pressure, or repeated-use failure also increases.

The regulatory framework may be stricter for medical devices, but its core questions are useful for any product that depends on sustained contact with the body.

• Can intended users apply or wear the product as designed?

• Does the product accommodate differences in anatomy, skin condition, dexterity, perception, and behavior?

• Are foreseeable workarounds treated as design inputs, or dismissed as misuse?

• Can users recognize when discomfort or visible skin change is becoming clinically meaningful?

• Does the product remain safe and functional during sweating, exercise, sleep, bathing, heat, humidity, and prolonged wear?

• Can it be removed, cleaned, adjusted, and reapplied without avoidable injury?

• Are complaints being converted into information that design and engineering teams can use?

  
  

These are not exclusively regulatory questions. They are design and product-quality questions.

For consumer wearable companies, the FDA framework offers a useful way to assess the real-world user interface. That interface includes not only the screen, app, or device controls, but also the biology of the skin on which the technology depends. It includes how users prepare the skin, apply the product, wear it through heat, sweat, pressure, and movement, remove it, clean it, and decide when and where to use it again. It also includes how users interpret and respond to prompts, alerts, visual displays, onboarding, and written care instructions.

Viewed this way, human factors becomes a way to connect product design with what the skin and the user actually do. It can strengthen internal design review, UI/UX research, change control, root-cause investigation, and postmarket surveillance. It can also help teams distinguish material problems from problems involving fit, pressure, friction, heat, the use environment, or user behavior.

The framework is not legally required for every product. But it offers a mature model for how thoughtful companies can organize risk, evidence, and design decisions. More importantly, many of the questions it raises should be built into the original engineering requirements rather than addressed only after a product reaches usability testing or the market.

The Skin-Contact System is Part of the Interface

For skin-worn products, the interface is not limited to the screen, app, or control system. It also includes every part of the product that touches, presses against, adheres to, heats, moves across, or is removed from the body.

That includes the adhesive, device geometry, backing, edge profile, strap, fit system, applicator, liner, overpatch, charging behavior, cleaning method, wear-time instructions, symptom guidance, and removal technique.

Each can influence whether the product remains comfortable, functional, and safe over its intended wear period.

Many organizations already have strong internal systems for material qualification, supplier controls, product testing, and conventional skin-safety assessment. Those controls remain essential. But real-world skin events often emerge from the interaction of several factors:

• material and adhesive properties;

• device size, mass, stiffness, edge design, and pressure;

• heat, moisture, occlusion, friction, and movement;

• the user’s anatomy, skin condition, expectations, and behavior;

• application, adjustment, reinforcement, charging, cleaning, and removal;

• repeated wear and limited site rotation;

• onboarding, labeling, app prompts, and troubleshooting;

• and the choices users make when a product lifts, hurts, itches, becomes warm, or causes visible skin change.

  
  

This is why passing biocompatibility or skin-safety testing does not end the discussion. It establishes one part of the safety story. Human factors examines how that story changes once the product leaves the laboratory and enters daily life.

What this Series Will Cover

This eight-part series will examine skin-worn products through the FDA human factors framework, with lessons for both regulated medical devices and consumer wearables.

Parts 1 through 6 follow the skin-contact workflow:

1. The skin-device interface as a human factors interface

2. Site selection

3. Skin preparation

4. Application, wear, and skin monitoring

5. Removal

6. Reapplication, site rotation, and cumulative skin injury

Each article will explain the relevant medical-device principles and then consider what consumer wearable teams can learn from the same approach.

Part 7 will examine FDA’s 2026 human factors submission guidance, including Human Factors Submission Categories 1, 2, and 3. It will also explore how the same structured thinking can support internal change-control, testing, and evidence decisions for consumer products, even when the FDA categories do not legally apply.

Part 8 will focus on what happens after launch. Postmarket complaints often arrive as a handful of vague words: “rash,” “burn,” “redness,” “pressure mark,” “allergy,” or “skin came off.” These descriptions are important, but they are not diagnoses. On their own, they rarely tell a company whether the root cause was allergic contact dermatitis, irritant injury, pressure, friction, heat, adhesive trauma, poor fit, incorrect use, or a product-design problem.

The final article will examine how these reports can be translated into clinically meaningful and design-relevant information.

From Skin to System: The BOHLD Approach

Skin safety and successful wear are not determined by materials alone. They are shaped by how a product is designed, fitted, prepared, applied, worn, monitored, adjusted, reinforced, removed, cleaned, charged, and reapplied under real-world conditions.

Biocompatibility and conventional skin-safety testing ask whether a material or finished product has the potential to produce an adverse biological response.

Human factors asks whether the complete product supports safe, effective, and sustainable use by real people.

At BOHLD, we work at the intersection of dermatology, human factors, skin safety, product design, and risk management. We help teams understand not only what happened on the skin, but how the full skin-contact system contributed to it and what can be improved.

That work includes translating dermatologic and human factors findings into practical guidance users can follow. BOHLD develops and reviews skin-preparation, application, wear, cleaning, removal, site-selection, rotation, and symptom-response instructions so that product guidance reflects both the biology of the skin and the way people actually use the device.

The goal is not simply to respond to skin events after they occur. It is to build skin safety, usability, and clear user guidance into the product from the beginning.