Better out than in? Not when it comes to Air Pods or Earwax

Material, Chemical, and Hygiene Considerations for Modern Ear-Worn Devices 

Headphones, airpods and earbuds are no longer simple consumer electronics. With being worn for longer, personal fitness integration, and the emergence of scientifically validated “hearing assistance” functions, they increasingly resemble medical-type devices. As a result, manufacturers face challenges to demonstrate not only acoustic performance, but material stability, chemical safety, and hygiene resilience under long-term exposure in the challenging ear canal environment.  

Key Environmental and Design Challenges: 

Human cerumen, otherwise known as earwax, contains lipids, fatty acids, salts, moisture, and cellular debris. Its high viscosity and stickiness allow it to infiltrate small device geometries, including:

- Softening or swelling of elastomers 

These effects contribute directly to acoustic drift, reduced microphone sensitivity, cleaning difficulty, and increased failure rates. Standard consumer electronics tests seldom replicate these effects. 

Long-term skin and ear canal contact introduces risks such as plasticiser leaching, pigment or additive migration, corrosion in salt-rich environments, and elastomer deformation. These phenomena may alter fit, sealing, and acoustic performance—particularly under conditions of heat, sweat, or charging-induced humidity cycling.

3. Extractables, Leachables, and Chemical Safety

As these products approach “quasimedical” safety standards, their testing increasingly uses medical device standards. ISO 10993-12 and ISO 10993-18, for example, are becoming increasingly used for evaluating chemical characterisation, extractables, and leachables. Thus, manufacturers demonstrate low toxicological risk and support global compliance. 

Earbuds frequently encounter microbial-rich environments. Device geometry, surface roughness, and port design influence biofilm formation and debris accumulation. The result: impaired acoustics, hygiene concerns, and user discomfort. Engineering strategies include surface optimisation, debris-resistant port architecture, and validated cleaning recommendations.

Wax-based occlusion is a major contributor to warranty returns and acoustic anomalies. Solutions such as hydrophobic coatings, internal and replaceable wax barrier filters, require standardised, repeatable testing to verify clogging resistance and longevity under simulated use. 

The Advantages of using Synthetic Cerumen as a Standard Test Medium 

To recreate the complex conditions of the ear canal, manufacturers rely on synthetic cerumen designed to replicate key chemical and physical properties of human earwax, for: 

Analytical techniques typically include ICP-MS, GC-MS, LC-MS, and exhaustive extraction methods, enabling early detection of potential material failures and verifying robustness prior to market release. 

Regulatory and Standards Context 

Ear-worn devices are influenced by medical device design and testing principles. Relevant standards and guidance include: 

Adopting these frameworks gives manufacturers confidence in material(s) selection, chemical safety documentation, and internationally accepted testing protocols. 

ESSLAB and Pickering Laboratories: Enabling Robust Device Evaluation 

ESSLAB, with over four decades of analytical laboratory experience, supplies ISO 17034-certified reference materials and consumables to support comprehensive testing workflows. Through collaboration with Pickering Laboratories, ESSLAB provides industry-standard synthetic biological matrices, including synthetic earwax with controlled viscosity, lipid profile, and deposition characteristics. 

These materials integrate seamlessly into ISO 10993-aligned extraction workflows, supporting: 

By enabling realistic and reproducible testing simulations, ESSLAB helps manufacturers reduce early-stage failures, strengthen QC programs, enhance acoustic reliability, and bring products closer to medical-grade performance expectations. 

As ear-worn devices become more sophisticated and more heavily used, their design challenges increasingly resemble those of clinical products. Validated testing with realistic ear canal simulations—including synthetic cerumen—is essential for ensuring safety, durability, and long-term performance. 

For more information on the Pickering range of artificial body fluids, please click here: https://esslabshop.com/collections/product-testing-solutions 

Or contact us at: https://www.esslab.com/ 

A Final - Word in Your Ear… 

As we continue to see technological advances in the engineering behind our ear-worn devices, it might also be a gentle reminder that we should give them a little more love (and cleaning) now and then. The ear canal is a warm, humid, microbiologically busy place—and your devices are right in the middle of it.  

And if you happen to be reading this over lunch, sandwich in one hand, phone in the other… perhaps spare a moment for another thought: how clean is your phone? Sometimes the smallest insights are the closest to home—and occasionally a little too close to the ear. 

References 

Biological evaluation of medical devices — Part 18: Chemical characterization of materials: 

https://nhiso.com/wp-content/uploads/2018/05/ISO-10993-18-2005.pdf 

Biological evaluation of medical devices — Part 12: Sample preparation and reference materials: https://nhiso.com/wp-content/uploads/2018/05/ISO-10993-12-2012.pdf