The benefits of quitting smoking on the skin

Kohei TAKAHASHI and his team sought to objectively assess the effect of quitting smoking on the appearance of the skin, particularly on the complexion. The content of carbonylated proteins in the stratum corneum, melanin, haemoglobin and the skin colour of the cheek and hand in 84 individuals aged between 24 and 77 were measured. The changes, before and during the smoking cessation treatment at 0, 2, 4, 8, and 12 weeks were compared and examined.

Protein carbonylation is induced by oxidative stress, and is considered one of the factors that alter the structure of keratin and reduce the transmission of light through the stratum corneum, thereby changing the appearance of the skin.

A downward trend in carbonylated proteins, both at the level of the cheek and the hand, was observed for each treatment period. However, the difference was not statistically significant. Nevertheless, skin clarity significantly increased and skin redness decreased on the hand 4 to 12 weeks after the start of treatment. Moreover, they did not observe any clear trend regarding melanin. A downward trend was observed for total haemoglobin (oxyhaemoglobin and deoxyhaemoglobin) between 2 and 4 weeks after the start of treatment.

What are the mechanisms involved?

In this study, no significant difference was observed in relation to carbonylated proteins, nor for melanin. The restoration of complexion after cessation of smoking would therefore be linked to haemoglobin, the protein responsible for oxygen transport in the blood. Studies have proven that the quantity of haemoglobin increases in the blood of smokers. When the level of haemoglobin is high, the blood can become more viscous, which makes the efficient circulation of red blood cells through the blood vessels more difficult.

This can lead to a reduction in blood flow to the tissues, and therefore a poor oxygenation which can compromise the cell renewal, and the accumulation of dead cells can cause a dull complexion. Thus, it is assumed that quitting smoking is capable of restoring the complexion's condition by reducing the levels of haemoglobin in the blood, and this as early as two weeks after quitting smoking.

Further studies are required to explore the associated mechanisms in detail.

Finn GOTTRUP and his colleagues measured the effect of smoking cessation on the epidermal healing of a wound and collagenase, the enzyme that breaks down collagen. To do this, skin fluid samples were taken from 48 smokers (aged 33, smoking 20 packs per day) and 30 people who had never smoked, and the epidermis was excised. Transepidermal water loss (TEWL) was measured after two, four and seven days, which increases during an injury, and decreases during the healing process. Subsequently, the smokers were randomly divided between continuous smoking or withdrawal with a nicotine patch. The sequence was repeated after 4, 8 and 12 weeks, and the levels of matrix metalloproteinase MMP-8 and MMP-1, and neutrophils in the fluid were evaluated by an immuno-enzymatic test.

One week after the injury, the TEWL (Transepidermal Water Loss) showed no significant difference between smokers and abstainers, respectively 17.20 g/cm2 per hour and 18.95 g/cm2 per hour. However, individuals who had never smoked showed a TEWL of 13.89 g/cm2 per hour. Consequently, the healing progression of abstaining smokers was similar to that of smokers and significantly slower than that of individuals who had never smoked.

However, in smokers, the level of MMP-8 was 36.4 ng/mL, compared to 15.2 ng/mL in those who had never smoked. The level of MMP-8 in abstinent smokers was 21.2 ng/mL, after four weeks of cessation. Therefore, the MMP-8 level in abstinent smokers was almost half that of smokers and was not significantly different from those who had never smoked. MMP-1 was not affected by smoking and abstinence. After abstinence, the number of neutrophils in the blood significantly decreased to the level of those who had never smoked. The correlation between MMP-8 and the neutrophil count is significant. Indeed, neutrophils produce MMP-8.

What are the mechanisms involved?

These results suggest a long-term impairment of healing in smokers, but a potential reversibility of extracellular matrix degradation four weeks after smoking cessation. Indeed, MMP-8 is a collagenase that limits the rate of degradation of fibrillar collagen I and III and is primarily released by polymorphonuclear neutrophils. Additionally, it is expressed by epidermal keratinocytes during healing. Type I collagen is abundant in the skin and scar tissue.

As an enzyme that breaks down collagen I, MMP-8 could potentially be involved in the tissue rupture mechanism as observed in smokers. It can be hypothesised that quitting smoking leads to a decrease in collagen degradation, and therefore a certain restoration of skin elasticity through the reduction of neutrophil levels and consequently MMP-8, but the effects on healing could be permanent.

Once again, additional studies may shed light on these results.

• GOTTRUP F. & al. Effect of smoking, abstention, and nicotine patch on epidermal healing and collagenase in skin transudate. Wound Repair and Regeneration (2009).

• CHIN H.W. & al. Changes in skin color after smoking cessation. Korean Journal of Family Medicine (2012).

• TAKAHASHI K. & al. Improvement in skin color achieved by smoking cessation. International Journal of Cosmetic Science (2012).