**5. Treatment**

If you suffer from relapsing HSV or you want to reduce the risk of the onset of HZ especially in summer, the most effective way is to avoid sunlight. Obviously, this is not always possible for most people. Even if someone deliberately avoids going to the beach, the face and other exposed parts of the body will still come in contact with direct sunlight throughout the day. What should be done to avoid solar radiation or minimize its effects?

## **5.1 Practical photoprotection strategy**

To minimize the risk of a HS recurrence it is necessary: to perform a gradual and progressive sun exposure; to know what garments to wear; to know the environmental conditions of exposure; to know each skin phototype; to use a protective product against UVB and UVA with SPF suitable for each phototype and environmental conditions. Sun exposure must be gradual and progressive. The ideal would be a tanning obtained with irradiation times that do not induce erythema for long periods, in order to activate mechanisms of natural photoprotection. In fact, it has been shown that sub-erythematous doses of UVB produce a tan. It is advised wearing long trousers and long-sleeved shirts during summer to

avoid exposing more skin than necessary to direct sunlight and also a hat to protect the face from direct sunlight and to prevent lips and face from coming into direct contact with UVR. However, a garment does not offer a complete UV barrier. If it is wet, it has less dry effect in stopping UV. Dark colors absorb more UVR, while clear colors are more effective against IR. Cotton has a low protective factor compared to silk and blue jeans. We must therefore choose thick and darker fabrics to have an effective protection such as blue jeans. The effects of solar radiation also vary according to environmental conditions. For example, the amount of UVR in the environment varies during the day (maximum value between 12 and 16), in the different months of the year (period with more irradiation June–July–August in the northern hemisphere), in relation to the altitude (the quantity increases by 6% every km of height) and at the latitude (greater quantity in the tropics). When the sky is uniformly covered there is a reduction of about 50% of the UVR compared to the clear sky, but if it is partially cloudy the irradiation is not uniform and may decrease or increase depending on the shape and properties of the clouds. In the environment, in addition to direct rays, also the reflected ones might be taken: the reflection is 80% on the snow (almost 100% if the snow is fresh and compact), 20% in the water, 17% on the sand and 3% on the grass. In addition, the water works as a lens and we must remember that if you are immersed up to 40–50 cm 5% of the rays affects us by reflection even on those parts of the skin (area under the chin, inside the arms, under the buttocks) which usually are not exposed. In addition, artificial UV exposure such as tanning beds and other devices that produce UVR should be avoided. The phototype indicates the ability to defend against the UVR that varies from individual to individual. It can be easily obtained taking into account the color of the complexion, the eyes and the hair and also the reaction of the skin to the sun exposure. The lower skin types (blond, red hair with fair skin that hardly tans) are those who do not adapt to sun exposure and are subjected to skin damage. It is also important to protect daily the skin and the HV recurrence zones with a sunscreen.

#### **5.2 Sunscreens**

Sunscreen is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's UVR and thus helps protect against sunlight.

Depending on the mode of action, sunscreens can be classified into physical sunscreens (i.e. those that reflect the sunlight) or chemical sunscreens (i.e. those that absorb the UVR). Chemical, organic sunscreens absorb over relatively narrow wavebands, mainly in the UVB but nowadays also extending into the UVA. Physical sunscreens are inorganic substances that reflect and scatter both UV and visible radiations [107]. Use of sunscreen can reduce chronic damaging and the carcinogenic effects of UV radiation and recurrence of cutaneous HV.

Currently, it is recommended to spread the sunscreen on the skin in two layers in such a way that its thickness is as close as possible to 2 mg/cm<sup>2</sup> , which is what enables to achieve the expected SPF. In practice, however, only between 0.5 and 1.5 mg/cm2 are used mostly because of the high price of sunscreen. The effect of application thickness is shown diagrammatically in 34 for the ideal scenario of uniform application. This demonstrates how light absorption depends strongly on thickness. For example, a sunscreen labeled SPF 16 is reduced to an SPF of 2 if the consumer applies 0.5 mg/cm<sup>2</sup> . Uniformity of application is another related crucial factor. The same amount of sunscreen non-uniformly applied implies that some areas receive little or no sunscreen. In general, sun lotions should always be applied in abundant quantities, in 2 layers and repeated during the day, immediately after swimming and every 2 h if sweating occurs. Only after a few days it will it be possible to reduce the SPF of the cream used, once the skin has had the time

**23**

provided the original work is properly cited.

\*Address all correspondence to: vmazza@uniss.it

No conflict of interests is declared.

*Sunlight and Herpes Virus*

normal MED is 30 mJ/cm2

**6. Conclusion**

**Acknowledgements**

**Conflict of interest**

**Author details**

*DOI: http://dx.doi.org/10.5772/intechopen.82643*

to activate its defense systems. Use of sunscreen should never be interrupted, even once tanned, because the melanin filters 70% of the UVB but not the UVA and because over time its filtered capacity becomes less effective. The SPF is important in the choice of a solar product and the one suitable for each phototype should be increased if environmental conditions require it. The SPF is the ratio of the dose of UV radiation causing minimal erythema in unprotected skin to the dose which causes a minimal erythema in skin protected by the sunscreen. For example, if the

SPF is 15. In other words, application of sunscreen has caused an increase by a factor of 15 in the dose required to induce erythema. The SPF is principally a measure of the sunscreen UVB attenuation. Although conceptually very simple, it is often misunderstood by the general public, who think that using a high factor sunscreen will protect the skin against the harmful effects of UV radiation. Even if the sunscreen provides the protection indicated by the SPF, a day's exposure outdoors wearing a factor 15 sunscreen will still result in more than one MED for many individuals. This misconception often leads individuals to stay in the sun longer than they should. There is also a major difference between the highly controlled conditions in

Sunlight is the most common trigger in stimulating the HSV reactivation. It still not well known how the UVR determines the reactivation of the virus. Several hypotheses have been made but do not lead to a single common path with the other triggers. However, we know how to protect ourselves from solar radiation and what

The authors thank Angela Sabalic for her precious collaboration and the prepa-

ration of the figure and Giustina Casu for native language check and editing.

the sunscreen laboratory and outdoor real-life product use. [107]

methods to use to avoid it or reduce its harmful effect on the skin.

and the MED of the protected skin is 450 mJ/cm2

, the

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Vittorio Mazzarello\*, Marco Ferrari, Stefano Decandia and Maria Alessandra Sotgiu Skin Lab, Department of Biomedical Sciences, University of Sassari, Sassari, Italy

#### *Sunlight and Herpes Virus DOI: http://dx.doi.org/10.5772/intechopen.82643*

*Human Herpesvirus Infection - Biological Features, Transmission, Symptoms, Diagnosis...*

avoid exposing more skin than necessary to direct sunlight and also a hat to protect the face from direct sunlight and to prevent lips and face from coming into direct contact with UVR. However, a garment does not offer a complete UV barrier. If it is wet, it has less dry effect in stopping UV. Dark colors absorb more UVR, while clear colors are more effective against IR. Cotton has a low protective factor compared to silk and blue jeans. We must therefore choose thick and darker fabrics to have an effective protection such as blue jeans. The effects of solar radiation also vary according to environmental conditions. For example, the amount of UVR in the environment varies during the day (maximum value between 12 and 16), in the different months of the year (period with more irradiation June–July–August in the northern hemisphere), in relation to the altitude (the quantity increases by 6% every km of height) and at the latitude (greater quantity in the tropics). When the sky is uniformly covered there is a reduction of about 50% of the UVR compared to the clear sky, but if it is partially cloudy the irradiation is not uniform and may decrease or increase depending on the shape and properties of the clouds. In the environment, in addition to direct rays, also the reflected ones might be taken: the reflection is 80% on the snow (almost 100% if the snow is fresh and compact), 20% in the water, 17% on the sand and 3% on the grass. In addition, the water works as a lens and we must remember that if you are immersed up to 40–50 cm 5% of the rays affects us by reflection even on those parts of the skin (area under the chin, inside the arms, under the buttocks) which usually are not exposed. In addition, artificial UV exposure such as tanning beds and other devices that produce UVR should be avoided. The phototype indicates the ability to defend against the UVR that varies from individual to individual. It can be easily obtained taking into account the color of the complexion, the eyes and the hair and also the reaction of the skin to the sun exposure. The lower skin types (blond, red hair with fair skin that hardly tans) are those who do not adapt to sun exposure and are subjected to skin damage. It is also important to protect daily the skin and the HV recurrence zones with a sunscreen.

Sunscreen is a lotion, spray, gel or other topical product that absorbs or reflects

Depending on the mode of action, sunscreens can be classified into physical sunscreens (i.e. those that reflect the sunlight) or chemical sunscreens (i.e. those that absorb the UVR). Chemical, organic sunscreens absorb over relatively narrow wavebands, mainly in the UVB but nowadays also extending into the UVA. Physical sunscreens are inorganic substances that reflect and scatter both UV and visible radiations [107]. Use of sunscreen can reduce chronic damaging and the carcino-

Currently, it is recommended to spread the sunscreen on the skin in two layers

are used mostly because of the high price of sunscreen. The effect of

. Uniformity of application is another related

enables to achieve the expected SPF. In practice, however, only between 0.5 and

application thickness is shown diagrammatically in 34 for the ideal scenario of uniform application. This demonstrates how light absorption depends strongly on thickness. For example, a sunscreen labeled SPF 16 is reduced to an SPF of 2

crucial factor. The same amount of sunscreen non-uniformly applied implies that some areas receive little or no sunscreen. In general, sun lotions should always be applied in abundant quantities, in 2 layers and repeated during the day, immediately after swimming and every 2 h if sweating occurs. Only after a few days it will it be possible to reduce the SPF of the cream used, once the skin has had the time

, which is what

some of the sun's UVR and thus helps protect against sunlight.

genic effects of UV radiation and recurrence of cutaneous HV.

in such a way that its thickness is as close as possible to 2 mg/cm<sup>2</sup>

**22**

**5.2 Sunscreens**

1.5 mg/cm2

if the consumer applies 0.5 mg/cm<sup>2</sup>

to activate its defense systems. Use of sunscreen should never be interrupted, even once tanned, because the melanin filters 70% of the UVB but not the UVA and because over time its filtered capacity becomes less effective. The SPF is important in the choice of a solar product and the one suitable for each phototype should be increased if environmental conditions require it. The SPF is the ratio of the dose of UV radiation causing minimal erythema in unprotected skin to the dose which causes a minimal erythema in skin protected by the sunscreen. For example, if the normal MED is 30 mJ/cm2 and the MED of the protected skin is 450 mJ/cm2 , the SPF is 15. In other words, application of sunscreen has caused an increase by a factor of 15 in the dose required to induce erythema. The SPF is principally a measure of the sunscreen UVB attenuation. Although conceptually very simple, it is often misunderstood by the general public, who think that using a high factor sunscreen will protect the skin against the harmful effects of UV radiation. Even if the sunscreen provides the protection indicated by the SPF, a day's exposure outdoors wearing a factor 15 sunscreen will still result in more than one MED for many individuals. This misconception often leads individuals to stay in the sun longer than they should. There is also a major difference between the highly controlled conditions in the sunscreen laboratory and outdoor real-life product use. [107]
