The Necessity of Sun Protection

Ultraviolet (UV) rays are the main cause of skin aging and damage. Long-term exposure to UV rays can cause skin darkening and sunburn, accelerate collagen loss, form wrinkles and spots, and even increase the risk of skin cancer. Therefore, sun protection is not only for skin whitening, but also a necessary measure to protect skin health.

The wavelength range of ultraviolet (UV) light typically spans 10–400 nanometers (nm). Depending on wavelength, UV light can be further divided into the following three primary bands:

‌‌1. UVA (long-wave UV): With a wavelength range of 315–400 nm, UVA has the strongest penetrating power, reaching the dermis layer of the skin. It is the primary cause of skin aging and tanning.

‌‌2. UVB (medium-wave ultraviolet rays): With a wavelength range of 280–315 nm, these rays have higher energy and primarily damage the skin's surface, causing sunburn and redness.

‌‌3. UVC (short-wave ultraviolet rays): With a wavelength range of 100–280 nm, these rays are almost completely absorbed by the ozone layer and typically do not reach the Earth's surface. Their effects on the skin are negligible.‌‌

Classification of Sunscreen Agents

Sunscreen agents in cosmetics are mainly divided into two categories: physical sunscreen agents and chemical sunscreen agents.

Physical Sunscreen Agents

Physical sunscreen agents, also known as inorganic sunscreen agents, are a type of white inorganic mineral powder. Common physical sunscreen agents include titanium dioxide and zinc oxide. These substances do not absorb ultraviolet rays but instead reflect and scatter them. When applied to the skin, they provide a physical barrier against ultraviolet rays, remaining on the skin's surface without being absorbed, which reduces the risk of skin irritation and helps prevent or mitigate skin damage caused by ultraviolet radiation. Cosmeceutical series (medical skincare series) tend to favor physical sunscreen agents. They are suitable for individuals with sensitive skin.

Principle: Physical sunscreen agents reflect or scatter UV rays to block UVA (which causes aging) and UVB (which causes sunburn).

Advantages: Physical sunscreen agents are gentle and non-irritating, suitable for sensitive skin and children.

Disadvantages: Physical sunscreen agents may leave behind a white cast.

Chemical Sunscreen Agents

Chemical sunscreen agents, also known as UV absorbers, are organic compounds that provide sun protection by absorbing harmful ultraviolet rays. Depending on the wavelength of radiation they protect against, UV absorbers can be divided into two types: UVA absorber and UVB absorber. The chemical molecules in chemical sunscreens are absorbed by the skin and may cause some irritation. Common chemical sunscreen agents include avobenzone, octocrylene, ethylhexyl salicylate, octinoxate, benzophenone 3, terephthalylidene dicamphor sulfonic acid, and others.

Principle: Chemical sunscreen agents absorb ultraviolet rays and convert them into heat energy for release.
Advantages: Chemical sunscreen agents are lightweight texture and refreshing feel on the skin.
Disadvantages: Some chemical sunscreen agents may irritate the skin, and putting on some more sunscreen every few hours is necessary.

SPF Value and PA Value

SPF (Sun Protection Factor) refers to UVB protection. The higher the value, the longer the protection against sunburn.

PA (Protection Grade of UV-A) refers to UVA protection. The more “+” symbols, the stronger the protection against tanning.