It is now well known how important it is to use high sunscreens to protect the skin from sun damage but there are still few studies that testify to the effects of ultraviolet radiation on the hair and scalp..
Solar ultraviolet radiation includes rays of3 different wavelengths:
UVA (320-400 nm), UVB (280-320 nm), UVCV (100-280 nm)..
Almost all UVC is absorbed by the Ozone layer, while UVA and UVB reach the Earth’s surface and impact the skin of humans.
UVB is almost completely absorbed by the epidermis while UVA reaches deeper into the dermis.
Schematically, the characteristics of the rays are as follows:
| UVA | UVB |
| Potentially less erythematous | More intense than UVA (x1000 ) |
| Low duration over the day | Potentially more erythematous (sunburn) |
| Able to penetrate clouds and windows | Variable intensity depending on the season and time of day |
| Penetrate deep into the skin | Low penetration into the skin |
| They are the major contributors to photoaging, oxidizing the already existing melanin
| Increase melanin synthesis |
| Indirect DNA damage via ROS (reactive oxygen species) | Direct damage to DNA |
What damage can excessive sun exposure cause?
The hair follicle is very sensitive to sunlight (therefore a combination of UVA and UVB) and this is demonstrated both by studies documenting an acute effluvium after sunburn of the scalp, and by studies showing a positive response of some pictures of alopecia to photodynamic therapy.
Depending on the intensity and wavelength administered, in fact, solar radiation has been shown on mice in vivo to reduce the cell proliferation of keratinocytes of hair follicles and to activate the degranulation of mast cells involved in perifollicular inflammation.
In a 2019 multicenter study, researchers exposed living donor-derived scalp pieces but different doses of UVA and UVB and studied the outcomes on hair follicles.
The results were clear: exposure to UVA and UVB results in a increase in cytotoxicity that is, the toxicity of hair follicle cells (measured by LDH assay), it also causes damage to the hair follicle epithelium and causes dystrophy of the same and finally inhibits keratinocyte proliferation and apoptosis of all hair follicle cells it also induces the catagen.
In essence sun exposure slows the processes of proliferation of hair cells and induces its entry into catagen or even programmed cell death..
How to protect your scalp and hair from the sun
It is therefore essential to implement a targeted photoprotection strategy for the hair.
The strategy should involve the use of headgear made of fibres with proven shielding capacity or the use of suitable topical sunscreens and could be accompanied by the use of oral supplements to provide protection from within.
Specifically in this area is a new combination of active derived from leaves of Rosemary of the Mediterranean (Rosmarinus officinalis) and from grapefruit (Citrus paradisii) titrated polyphenols.
This combination exhibits antioxidant activity capable of quenching and/or eliminating oxidizing oxygen species and ppreventing cellular malfunction that might otherwise have cytotoxic and carcinogenic effects.
This combination of actives also has anti-inflammatory activity that is essential to inhibit subsequent tissue damage that occurs after the irradiation process.
Rosemary and citrus polyphenols show significant absorption within the UVB range.
The above mentioned actives play a protective action towards DNA because they reduce the breakage of the double helix following UV exposure and play a protective role towards keratonocytes and dermal matrix cells.
We must therefore remember to always photoprotect our skin and our hair by wearing a hat, the most suitable sun filter spray for our hair and by taking the most suitable photoprotection by mouth.
Bibliography:.
Nobilr V et al Skin photoprotective and atiageing effects of a combination of rosemary and grapefruit polyphenols. Food Nutr Res 2016.1;60:31871
Sanchez a et a Protective effects of citrus and rosemary extracts on UV induced damage in skin cell model and human volounteers.
J Photochem Photobiol B. 2014. 5;136:12-8
Trueb, R.M. The impact of oxidative stress on hair. Int. J. Cosmet. Sci. 37(Suppl 2), 25- 30 (2015).
Trueb,R.M.Effectofultravioletradiation, smoking and nutrition on hair. Curr. Probl. Dermatol. 47, 107-120 (2015).
Franca, K., Castillo, D., Tchernev, G. and Lotti, T. UVA-1 in the treatment of alopecia areata. Dermatol. Ther. 30, e12547 (2017).
Braun, S., Krampert, M., Bodo, E. et al. Keratinocyte growth factor protects epidermis and hair follicles from cell death induced by UV irradiation, chemotherapeutic or cyto-oxic agents. J. Cell Sci. 119, 4841-4849 (2006).
