Ultraviolet (UV) radiation has significant effects on human skin—both short-term and long-term—depending on the wavelength, intensity, and duration of exposure. The primary sources of UV radiation are sunlight and artificial sources like tanning beds.
Types of UV Radiation That Affect Skin:
- UVA (315–400 nm): Penetrates deep into the dermis; responsible for aging and long-term damage.
- UVB (280–315 nm): Affects the epidermis; causes sunburn and direct DNA damage.
- UVC (100–280 nm): Mostly absorbed by the ozone layer and does not reach the Earth’s surface.
Short-Term Effects:
1. Sunburn (Erythema)
- Mainly caused by UVB exposure.
- Skin becomes red, painful, swollen, and may blister.
- Indicates acute inflammation due to DNA and cellular damage.
2. Tanning
- A defensive response where skin increases melanin production to absorb UV rays.
- Temporary darkening but does not prevent long-term damage.
3. Photosensitivity
- Some individuals experience allergic-like reactions or rashes under UV exposure, especially when taking certain medications.
Long-Term Effects:
1. Premature Aging (Photoaging)
- Caused mostly by UVA.
- Leads to wrinkles, sagging, rough texture, and pigmentation changes due to damage to collagen and elastin fibers.
2. Skin Cancer
- Prolonged UV exposure can damage DNA, leading to:
- Basal cell carcinoma
- Squamous cell carcinoma
- Melanoma (most aggressive form)
- UVB is the major contributor, though UVA also plays a role.
3. Pigmentation Disorders
- Includes freckles, age spots, and uneven skin tone due to changes in melanin distribution.
Protective Mechanisms of the Skin:
- Melanin absorbs UV radiation and protects deeper layers.
- Thickening of the outer skin (stratum corneum) as a barrier.
- DNA repair enzymes, though not always fully effective with high exposure.