Design elements in face masks can provide an effective fit to prevent droplet spread: A reply to “Importance of nose wires in face masks”

To the Editor: I appreciate the interest of Kassamali et al¹ in my article and am writing in response to the concerns raised. Mask-wearing recommendations to prevent the spread of the contagion must be driven by evidence supporting the complex phenomena of droplet or airborne spread, reflecting the aerodynamic trajectories and practicalities that affect their compliance. Textile-skin friction and discomfort or pain sensations are likely to impact the course of dermatoses via a neuroimmune interface, relevant to skin ecobiology.

Accessories predispose patients to frictional dermatoses. Although surgical masks provide an adjustable fit, their moldable pieces confer an incomplete seal. The value of a nose wire in the context of a fabric face mask (inherently, a nonpersonal protective equipment standard) is uncertain and may affect an individual's compliance.

A contoured, bipaneled design at the nose-cheek junction is close fitting and minimizes friction and leakage when designed with a user-adjustable ear loop (Fig 1 ). Water resistance and a design providing maximum coverage or minimum displacement are critical features for a close catchment area around the orifices. A bilayer fabric mask with synthetic textiles is valuable for increasing moisture resistance (Fig 2 ). Maximum surface area coverage over facial contours, ie, the jawline and nose bridge, provides a “natural” pressure-free drape covering the orifices.

Fig 1.

Bipaneled mask with a contoured design at the nose-cheek junction achieves a close fit without additional accessories when fitted with an adjustable ear loop.

Fig 2.

Water-resistance contributes significantly to a mask designed to minimize droplet spread to the environment. Here, a bilayer, reusable fabric mask made from synthetic fabric is compared with a disposable surgical mask (PPE standard with waterproof meltblown layer). Approximately 34 drops were released over a duration of 34 seconds onto the fabric, without any leak observed, presumably simulating its ability to catch salivary droplets while speaking. PPE, Personal protective equipment.

Adequate air flow for speaking and breathing prevents uncomfortable “mask collapse” due to changes in pressure within the mask-enclosed space (Fig 3 ). A durable fabric of appropriate weight holds its 3-dimensional shape in this design without additional accessories. Maintaining breathability and air flow improves the compliance of mask use while speaking, an important activity that aerosolizes respiratory droplets. An approximate fit gauge of 1 finger-breadth gap laterally allows comfortable movement of the jaw, with minimal friction and displacement while speaking (Fig 4 ). Discomfort increases the incidence of mask handling or contamination.

Fig 3.

Adequate air flow for speaking or breathing prevents uncomfortable “mask collapse” due to changes in pressure within the mask-enclosed space. This minimizes displacement and handling, which increases the risk of contamination.

Fig 4.

Maximum skin surface area coverage at the jawline and cheeks for 3-dimensional drape over the orifices to minimize textile-skin friction and displacement.

The purpose of recommending wearing mask in public must be clearly defined, ie, to limit the environmental spread of biofluids,² which impact viral load or the risk of infectivity via airborne transmission.³ The inherent protective value (against infection) of wearing individual fabric mask in a non-N95/full personal protective equipment setting must be carefully considered. Current evidence points toward the value of wearing fabric face mask in the context of the entire population being masked up over prolonged periods of daily indoor or outdoor activities.

Adding layers, ie, “double masking” is expected to improve mechanical blockage but will affect comfort or compliance. It may also not communicate the complex phenomena of airborne transmission (ie, via ocular exposure)⁴ and important environmental factors (physical distancing, outdoor or indoor, and particulate matter interactions). Face visors over a face mask may be of value by providing an additional physical barrier in the droplet trajectory and reducing the environmental contagion. Plastic visors can be disinfected or reused and may minimize the touching of mask surfaces. Reverse “double masking,” ie, biofunctional textile masks under a disposable surgical mask, may alleviate the symptoms of mask-induced dermatoses, exacerbated by disposable masks. Biofunctional textiles can destabilize infectious viral droplet nuclei via biocidal effects,^{5 , 6} thereby reducing fomite contagion. Correct storage or handling must be emphasized,² while addressing its practicalities in a layperson context. The added value of wired masks should be researched in the context of aerodynamic models measuring the droplet trajectories while speaking.

Conflicts of interest

The author is the chief scientific advisor and owns Dr. TWL Dermaceuticals, a cosmeceutical, biofunctional textile research and development company.