Exposure to nanomaterials through the skin

Nanomaterials are widely used in many industrial processes and incorporated in numerous consumer products such as cosmetics, pharmaceuticals, stain-resistant and antibacterial clothing, sports equipment, and cleaning products. The use of nanomaterials in these products can potentially lead to exposure, penetration, and absorption into the body through the skin, particularly for workers and consumers.

Although the skin is relatively impermeable to nanomaterials, systemic exposure is still a concern since the skin is one of the largest organs of the human body and there is still debate in the scientific community regarding the ways in which nanomaterials interact with the skin and their potential to cause adverse health effects. As the dermal absorption of nanomaterials is a pre-requisite for any systemic availability following dermal exposure, it is very important to clarify the mechanisms by which they can be absorbed through the skin and what are the factors influencing dermal absorption of nanomaterials.

Skin integrity plays a significant role in the absorption of nanomaterials 

Skin absorption and penetration is a complex interplay between the properties of the particles in the formulation and the skin condition.  Compromised skin integrity and formulations that increase permeability of the skin appear to increase penetration. 

Nanoparticles tend to aggregate in sweat, which may reduce their ability to penetrate the outermost layer of the skin, the stratum corneum. However, penetration may still be higher for particles that are used in a formulation that prevents their aggregation. 

Smaller size may mean higher absorption

Several studies suggest that particle size may impact skin penetration, with smaller particles having greater penetration rates. Surface properties like coating and surface charge, with a positive charge leading to higher penetration, may also influence the dermal penetration of particles.

More comparable studies needed on skin absorption

To shed light on the relationship between nanomaterial properties and their potential for skin absorption, more comparable studies are needed. The relationship between nanomaterials and their dispersion or formulation during exposure is highly complex and can vary for a single nanomaterial, depending on the formulation that is used.