Everyone is Talking About: Silk Pillowcases

EVERYONE IS TALKING ABOUT: SILK PILLOWCASES

Silk pillowcases and scrunchies have long been considered a way of preventing hair damage during sleep and styling, and in recent years the benefits of silk pillowcases have expanded to include skin-based claims. A quick online search reveals that there are two main claims-categories for these items:

1. Minimizing friction between skin or hair and the pillowcase, which is reported to reduce frizz, tangles and breakage for hair, and prevent creases and wrinkles for skin.

2. Moisture retention, which is claimed to keep hair looking hydrated and healthy and keep skin looking youthful and plump.  

But is there any truth in either of these claims? This short article will take look at evidence. 

Claim 1: Minimize friction

If there is a large coefficient of friction between two surfaces it stands to reason that the possibility of damage to either one or both surfaces, through one passing over the other, is increased because of the larger forces needed to effect movement. When it comes to hair and skin this will also hold true: exposure of hair fibers or skin cells to lower friction materials (e.g. pillowcases and hair scrunchies) should result in less snagging and therefore a lower risk of physical damage to either. Let’s look at hair first.

When looking at the interaction of hair with a pillowcase, the important factor to consider is the ‘slipperiness’, or friction coefficient, between the pillowcase material and the hair fiber. This can be measured through use of a hair friction test, where  a tress is pulled between two fabric surfaces gently pressed together, with work undertaken by TRI showing that silk has a lower friction coefficient with hair than cotton. Taking this further, our rotating head set-up allows investigation into the breakage of hair fibers after exposure to different materials, such as cotton or silk – simulating a night of sleep – as well as hair volume, frizz and curl definition, enabling a direct comparison between textile materials under controlled conditions. 

However, the material that hair is exposed to is only half the story. Work by Bowen and co-workers has shown that the tribological properties of hair fibers themselves are impacted by the presence or absence of sebum or conditioners: hair fibers with either sebum or conditioner product present exhibited initial coefficients of friction against a probe at least 25% lower than fibers without. The team also showed that directionality in terms of force application – either ‘with the cuticle’ or ‘against the cuticle’ – was important: the larger forces required for movement of fibers ‘against’ the direction of the cuticle caused more damage. 

When it comes to skin, the medical profession has noted the low friction coefficient of silk against the skin, and some doctors recommend the use of silk clothing as a non-pharmacological treatment for skin conditions. And this isn’t urban legend, it’s been proven under closely controlled conditions: one clinical trial has shown that for sufferers of topic dermatitis (AD), wearing silk clothing can be an effective treatment that doesn’t require pharmaceutical-based intervention. However, whether or not there is any impact upon wrinkles and sleep creases is still unknown. 

Conclusion: TRI has shown that there is a lower friction force between silk and hair than cotton and hair. In medicine, silk is known to have smooth fibers that don’t irritate the skin and silk clothing can be an effective treatment for AD. Overall, evidence suggests that silk may help avoid friction-based damage of hair and skin. 

Claim 2: Retain hydration

The ability of a material to ensure either skin or hair maintains hydration can arguably be linked with how much moisture the material absorbs itself. Both cotton and silk are naturally hydrophilic in character, therefore absorb water. In a study looking at the sweat evaporation from clothing, Otomasu and co-workers showed that cotton absorbs more water than silk and transmits water through the fabric more quickly. In this case, it could reasonably be concluded that the higher water absorbency of cotton compared with silk might cause water to leave hair or skin more quickly when exposed to cotton bedding, which may cause dryness or dehydration. 

Conclusion: data suggest that silk absorbs less water than cotton, so it is possible that silk can help maintain skin and hair moisture levels but the results are far from definitive. 

Overall, it looks like there may be a grain of truth in the claims relating to silk protecting hair and skin from mechanical damage, as well as helping avoid dehydration. However, further studies would be useful to probe these tentative differences. 

Contact TRI today to see how we can help you design and execute studies looking at the interaction of hair and skin with different materials.