Pigment change

Anti-Pollution Matrix > Damage > Clinical > Pigment change

Explanation

Melanin is a natural pigment that occurs in the skin, hair and eyes and influences their coloration. The pigment is formed by melanocytes, which are localized in the epidermal basal cell layer of the epidermis and the hair follicles.

Two types of melanin can be distinguished:

• the brownish-black eumelanin
• the yellow-reddish pheomelanin

Primarily, melanin production is a protective mechanism. Through the production of melanin by melanocytes, an endogenous protection is generated, which should protect the skin cells, but especially their nucleus, from irradiation-induced changes in the genetic material. After the absorption of a photon, the melanin molecules are transformed into an energetic state. The absorbed energy is converted into thermal energy, which is thought to prevent cell damage [1]. Vierkotter et al [2] were able to show that increased skin pigmentation can be caused not only by irradiation but also by increased air pollution, which additionally correlated with increased skin aging. Pigment spot formation was more pronounced, compared to wrinkle formation.

A direct correlation between topical exposure of the skin (ex vivo and in vivo) to diesel exhaust mixtures of non-toxic concentration and increased melanin production as a stress response was demonstrated [3].

 

Effects on the skin

Normally, melanin gives the skin an even pigmentation (= tanning).

Increased sun exposure, environmental pollutants, but also hormonal influences or skin aging can result in the development of hyperpigmentation (accumulation of pigment or age spots).

 

Measures

Increased sun exposure, pollution concentration, etc. should be avoided to counteract the development of oxidative stress/free radicals. Sunscreens, as well as textile protection can counteract the formation of free radicals and thus the formation of pigment spots.

In cosmetics, creams containing skin lightening substances are also used to correct irregular pigmentation or age spots.

In general, the use of antioxidants is helpful to neutralize free radicals.

 

Impact detection methods

A melanin meter can be used to determine melanin density in skin (in vivo / ex vivo) [4].

Hyperspectral imaging can also be used to determine the melanin content in tissue in vivo.

Histological examinations can be used to investigate melanin content in skin explants, and quantification of melanin content from cellular/and or skin lysates can be done by absorbance. Masson-Fontana staining or Warthin-Starry staining can be used for this purpose.

Chromameter measurement can also give an indication of increased melanin content in the skin. The L* value in the L*a*b* color space is then lower.

Image-analytical color measurement can be used to quantify pigment spots [5].

 

References

[1] M. Brenner, V.J. Hearing, The protective role of melanin against UV damage in human skin, Photochem Photobiol, 84 (2008) 539-549, DOI: 10.1111/j.1751-1097.2007.00226.x
[2] A. Vierkotter, T. Schikowski, U. Ranft, D. Sugiri, M. Matsui, U. Kramer, J. Krutmann, Airborne particle exposure and extrinsic skin aging, J Invest Dermatol, 130 (2010) 2719-2726, DOI: 10.1038/jid.2010.204
[3] J. Krutmann, [Air pollution and the skin], Hautarzt, 70 (2019) 156-157, ·  DOI: 10.1007/s00105-018-4349-5
[4] T. Dwyer, H. K. Muller, L. Blizzard, R. Ashbolt, G. Phillips, The use of spectrophotometry to estimate melanin density in Caucasians. Cancer Epidemiol Biomarkers Prev. 1998 Mar;7(3):203-6. https://pubmed.ncbi.nlm.nih.gov/9521433/
[5] Bielfeldt, S., Springmann, G., Seise, M., Wilhelm, K. P., & Callaghan, T. (2018). An updated review of clinical methods in the assessment of ageing skin–New perspectives and evaluation for claims support. International journal of cosmetic science, 40(4), 348-355. https://doi.org/10.1111/ics.12484