Understanding UVA Rays: Effects on Skin and Choosing Effective Sun Protection

Understanding UVA Rays and Their Effects on Skin

The sun emits three main types of ultraviolet rays - UVA, UVB, and UVC. Of these, UVA rays have the longest wavelength and are able to penetrate deep into the skin. While UVB rays are primarily responsible for sunburn, UVA rays play a major role in skin aging and wrinkling. They can also damage skin cells and suppress the immune system, making UVA a major contributor to skin cancer.

What are UVA Rays?

UVA stands for ultraviolet A rays. These rays have wavelengths between 320 and 400 nanometers, making them longer than UVB rays (290-320 nm) and shorter than UVC rays (100-290 nm). UVA rays can penetrate clouds and glass, allowing them to reach the skin even on overcast days or when you're driving a car or sitting indoors next to a window.

UVA radiation constitutes up to 95% of the UV radiation that reaches the Earth's surface. Because of their longer wavelength, UVA rays are able to penetrate deeper into the skin than UVB rays. While UVB rays affect only the outer layer of skin, UVA penetrates into the thickest layer of the epidermis as well as the dermis below it.

Damaging Effects of UVA

Here are some of the damaging effects of UVA exposure:

• Skin aging - UVA rays contribute to premature aging through wrinkling and age spots.
• Immune suppression - UVA damages skin cells called Langerhans cells that are part of the immune system defenses in skin.
• Skin cancer - UVA radiation induces DNA damage and oxidative stress, leading to melanoma and non-melanoma skin cancers.
• Eye damage - Overexposure to UVA rays may contribute to certain eye diseases such as cataracts.

While UVB rays cause obvious sunburns, UVA damage is often invisible, occurring gradually over time with repeated exposures. For this reason, UVA rays have sometimes been called the "silent killer."

Differences Between UVA and UVB

Here are some key differences between UVA and UVB rays:

• UVB rays have shorter wavelengths (290-320 nm) than UVA (320-400 nm).
• UVB is primarily responsible for sunburn while UVA contributes to skin aging.
• UVB does not penetrate glass while UVA rays penetrate glass and clouds.
• UVB is mainly intense during midday hours while UVA rays are equally intense during all daylight hours.
• UVB is mostly filtered by the ozone layer while less UVA is filtered.

Choosing Effective Broad Spectrum Sun Protection

To protect yourself from the harmful effects of UVA and UVB rays, it's important to use "broad spectrum" sunscreen that provides protection from both UVA and UVB. Here's what to look for when choosing sun protection:

1. Broad Spectrum Labeling

The FDA regulates sunscreens in the United States and mandates that they should pass broad spectrum testing before being labeled as such. Broad spectrum means the sunscreen provides protection against both UVA and UVB.

2. SPF 30 or Higher

SPF (sun protection factor) is a measure of a sunscreen's UVB protection. Higher SPF numbers indicate more UVB protection. For adequate protection against UVB, a sunscreen should be SPF 30 or greater.

3. UVA Protection

For UVA protection, look for sunscreens containing ingredients like avobenzone, oxybenzone, zinc oxide, titanium dioxide, or ecamsule. Sunscreens labeled "broad spectrum" must contain filters that protect against UVA.

4. Water Resistance

If you plan to sweat or swim, choose a sunscreen labeled "water resistant" which must retain its SPF after 40 minutes in water. "Very water resistant" sunscreens last up to 80 minutes.

5. Application Tips

To get full sun protection, be sure to apply enough sunscreen - about 1 ounce per sitting to cover all exposed skin. Reapply every 2 hours and after swimming or sweating. Wear protective clothing and seek shade when possible.

Ingredients to Look for in Broad Spectrum Sunscreens

There are several FDA-approved active ingredients in sunscreens that provide broad spectrum protection against UVA and UVB.

Mineral Sunscreen Active Ingredients

• Titanium dioxide - Reflects and scatters UV radiation.
• Zinc oxide - Absorbs and scatters UV radiation.

Chemical Sunscreen Active Ingredients

• Avobenzone - Absorbs UVA rays.
• Oxybenzone - Absorbs UVA and UVB rays.
• Octisalate - Absorbs UVB rays.
• Homosalate - Absorbs UVB rays.
• Octocrylene - Absorbs UVB rays.
• Ecamsule - Protects against UVA rays.

Some sunscreens combine multiple active ingredients to provide broad spectrum protection. Read sunscreen labels closely to ensure you are getting UVA and UVB protection.

Understanding Sunscreen Terminology

Sunscreens come with a host of terminology on their labels that indicate their effectiveness. Here are some common terms explained:

UVA with Circle Logo

The UVA with circle logo indicates the sunscreen meets EU standards for UVA protection. To carry this logo, the product must provide a UVA protection factor that is at least 1/3 of the SPF.

Broad Spectrum

Broad spectrum means the sunscreen provides protection against both UVA and UVB rays. All sunscreens should be broad spectrum.

SPF

SPF stands for sun protection factor, a measure of UVB protection. Higher SPFs indicate more protection against sunburn.

Water Resistant vs Waterproof

Water resistant sunscreens must retain SPF after 40 minutes in water. Very water resistant holds SPF for 80 minutes while swimming or sweating.

No sunscreens are waterproof, only water resistant, so reapplication is necessary after swimming or sweating.

Photostable

Photostable sunscreens retain effectiveness when exposed to sunlight. Many ingredients break down in UV light.

FAQs About UVA Rays

What is the difference between UVA and UVB?

UVA rays have longer wavelengths and penetrate deeper into skin than UVB rays. UVA contributes to skin aging while UVB causes burning.

What are the health effects of UVA rays?

Overexposure to UVA radiation can lead to premature skin aging, wrinkles, age spots, and in severe cases, skin cancer. UVA can also suppress the immune system.

Do UVA rays penetrate glass?

Yes, unlike UVB which is blocked by glass, UVA rays are able to penetrate through glass windows. UVA can reach your skin even while driving or sitting indoors.

Do UVA rays cause cancer?

Yes, UVA radiation is carcinogenic and contributes to both melanoma and non-melanoma skin cancers. UVA causes DNA damage that can lead to cancerous mutations.

How can I protect myself from UVA exposure?

Wear broad spectrum sunscreen with SPF 30 or higher, seek shade when possible, wear protective clothing, hats and sunglasses, and avoid excessive sun exposure to protect your skin from UVA.

The Importance of UVA Protection

UVA rays make up the vast majority of ultraviolet radiation that reaches the Earth and penetrates deep within the skin. Overexposure to these rays leads to signs of premature aging including wrinkling, age spots, and leathering in addition to suppressing immunity and potentially causing skin cancer.

That's why it's critical to protect yourself with broad spectrum sunscreen containing ingredients that specifically absorb UVA wavelengths. Seek shade when the sun is most intense, cover up with hats, sunglasses and protective clothing, and be vigilant about sun safety to guard your skin from the damaging effects of UVA.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.