Sunscreen - Ideal Properties, Factors, Risks, and Benefits

What Are the Ideal Properties of Sunscreen?

A chemical sunscreen should be inert, non-irritant, stable, and compatible with other ingredients. Physical sunscreen should be easily spreadable, aesthetic, smaller particle size, waterproof, soluble, and non-odorous. Functionally it should protect across broad wavelengths and limit systemic absorption. In addition, the products should be readily available, affordable, and contaminant free.

What Are the Factors That Strongly Influence When Using Sunscreen?

1. Inorganic vs Organic Sunscreens:

Organic sunscreens are the basis of sunscreen formulation. It includes derivatives of Anthranilates, Benzophenones, Camphor, Cinnamates,Dibenzoyl methane, P-aminobenzoates, or Salicylates. Inorganic sunscreens are harmless pigments that cannot penetrate the skin. The two most common inorganic sunscreens are Titanium dioxide (Ti02) and Zinc oxide (ZnO).

Recommendation: A broad-spectrum sunscreen with UVA and UVB filters is recommended, irrespective of whether the ingredients are organic or inorganic. When using sunscreens with predominantly macro inorganic filters, it is more important to apply an adequate amount since underapplication is very common.

2. Water-Resistant Sunscreens:

Water-resistant sunscreen determines the binding ability of the sunscreen to the skin and withstands adverse conditions like sweating, swimming, friction, and removal through any physical contact. Apart from water resistance, rub-resistant properties also affect the sun-protective effect of sunscreens.

Recommendation: Water-resistant sunscreen must be worn in conditions like profuse sweating, water immersion, increased skin rubbing through physical contact, or sand contact. Sunscreen should be immediately reapplied to compensate for the loss of sunscreen after any of these activities.

3. Lip Protection:

Lip protection is an essential part of sun protection practices. UV radiation increases the risk for the development of lip cancers. UV filters are now available in various commercial products like lip gloss, lip balm, and lipstick. The use of sun-protective lip products decreases the risk of lip cancers. An application thickness of 1 mg/cm square is considered adequate for sun protection.

Recommendation: Lip sun protective products must be applied generously to cover the lip entirely. The use of SPF greater than 30 and reapplying is recommended to compensate for under the application.

4. Amount of Sunscreen:

The recommended application is 2 mg/cm square of sunscreen or 35 mL per application to sufficiently cover 1.73 meter square of adult body surface area. Controlled devices like pumps or squeeze bottles usually expel higher quantities.

Recommendation: Sunscreens must be applied copiously to all sun-exposed areas. Practically, 45 ml - the amount of one shot glass is more than enough for the entire body surface of an average-sized individual, or one to two teaspoons for the face and neck and two to three tablespoons for the body.

5. Frequency of Application:

It is advised to reapply sunscreen. Sunscreen with SPF 15 - SPF 30 should be reapplied after three hours. A single application of sunscreens in a hot environment, physical activity, and bathing for eight hours reduces erythema caused by UVB. The resultant recommendation is reapplying 15 minutes - 30 minutes after sun exposure to exposed sites after sun exposure and vigorous activity like swimming and excessive sweating or rubbing. Interestingly, sunscreen with SPF 30 accumulates in the skin when applied three times daily, providing a higher SPF.

Recommendation: If an adequate amount of sunscreen is applied first, reapplication is necessary only after activities that remove the sunscreen layer like swimming, sweating, and rubbing. There is no specific frequency to reapply regularly.

6. Sun-Protection Factor of Sunscreens:

The ideal SPF is difficult to define. Currently, broad-spectrum sunscreens with SPF values of 30 or greater are recommended. However, after sun exposure SPF 100+ sunscreen was more effective in protecting against sunburn.

7. Sun-Protection Factor and Application of Sunscreen:

The recommended amount of application of sunscreen is 2mg/cm square. It is noted that people apply 20 % to 50 % less sunscreen than the normal range. That SPF value drops with the inadequate application. Hence, a sunscreen with SPF greater than 50 is preferred to compensate for the insufficient sunscreen application.

Recommendation: Generally, water-resistant sunscreens with higher SPFs are W/O emulsions, while those without water-resistant properties are O/W emulsions. However, people prefer O/W as it is lighter and has non-comedogenic properties.

8. Expiry Date:

It is recommended to use sunscreen within the expiry date to avoid maltreatment. Most sunscreen manufacturers provide a period after opening (POA) of 12 months. However, when placed in temperatures between −20°C and 60°C for eight hours, few sunscreens show discoloration and phase changes at the extremes of temperatures.

Recommendation: Sunscreens must be stored at room temperature to safeguard stability. There is less evidence to claim whether it is unsafe or safe to use sunscreens after the manufacturers’ specified expiry date.

9. Application Before Sun Exposure:

Recommendation: Sunscreen should be applied 15 minutes - 30 minutes before sun and water exposure.

What Are the Risks and Benefits of Using Sunscreen?

There has been a lot of controversy about the harmful effects of sunscreen.

More safety and efficacy data are as follows:

Twelve organic chemical ingredients Cinoxate, Ensulizole, Dioxybenzone, Homosalate, Meradimate, Oxybenzone, Octisalate, Octocrylene, Octinoxate, Padimate O, Sulisobenzone, and Avobenzone are safe, yet it more information is needed. Inorganic physical ingredients, Titanium dioxide, and Zinc oxide are considered safe, whereas PABA and Trolamine salicylate are unsafe for use in sunscreens. Chemical ingredients like Benzophenone (BP) - 3, Octyl methoxycinnamate, and Octocrylene can cause photoallergic contact dermatitis; Benzophenone causes estrogenic and antiandrogenic activity; BP-2 and 4- Hydroxy benzophenone can diminish fertility and delay pregnancy; high levels of BP-3 exposure can increase male birth weight, decrease female birth weight and male gestational age.

Recommendation: The skin surface is an effective barrier and does not allow penetration of physical ingredients like Zinc and Titanium dioxide nanoparticles. Therefore, systemic absorption is not a concern. The common side effect of chemical sunscreens is light allergy.

Are Sunscreens Safe for Infants?

Sunscreen is recommended only for children above six months after consulting with a child specialist. Avoiding the sun and wearing protective clothing are primary sun safety measures below six months. Apply sunscreen only to small areas where clothes cannot cover, like the face, neck, or back of the hands, and wash off when sun protection is not required. The recommended SPF is between 15 to 30.

Recommendation: There is no clear evidence of the harmful effects on the mechanism of action of sunscreens in infants. It is reasonable to limit sunscreen use in children younger than six months as their skin is immature, and the nanoparticles get absorbed easily. Sun protection for infants should be a behavioral modification such as avoiding the outdoors during sunny hours, seeking shade, and wearing protective clothing.

Does Sunscreen Prevent Skin Damage?

Increasing UV exposure contributes to skin aging. Regular sunscreen application protects from skin aging signs like pigmentary changes, rhytides, and telangiectasias. In addition, moisturizers with broad-spectrum sunscreen protect against the sun’s UV - induced skin damage on the top skin surface and UVA radiation-induced gene change. This directly affects skin aging and the skin’s stress defense response.

Recommendation: There is substantial literature evidence that sunscreens prevent skin aging.

Does Sunscreen Prevent Skin Cancer?

After an extended follow-up, daily sunscreen decreased almost 40 % of squamous cell carcinoma and basal cell carcinoma. It also prevents and delays the development of solar keratoses.

Recommendation: Regular application of sunscreen can prevent melanoma and non-melanoma skin cancers.

Conclusion:

Sunscreens are widely used topical sun protection agents. Using broad-spectrum UVA and UVB sunscreen with a minimum SPF of 30, applied generously to all sun-exposed areas, can slow down the skin aging process and prevent skin cancer. In addition, choosing higher SPF and water-resistant sunscreen during physical activity can avoid reapplication.