Sun Protection

Why sun protection matters

UV radiation damages the DNA in skin cells. Two types matter most:

• UVB causes sunburn and is a major cause of skin cancer.
• UVA penetrates deeper, causes skin aging and contributes to skin cancer. It passes through clouds and window glass.

Over time, UV damage leads to:

• skin cancers: basal cell carcinoma, squamous cell carcinoma and melanoma. Skin cancer is the most common cancer in the US
• actinic keratoses: rough precancerous patches
• photoaging: wrinkles, sun spots, loss of elasticity
• eye damage: cataracts and growths on the eye surface

A history of blistering sunburns, especially in childhood, greatly increases melanoma risk. Tanning beds are classified as a cause of cancer, and their use before age 35 substantially increases melanoma risk.

The UV index

The UV index forecasts the strength of UV radiation on a scale from 0 to 11 or higher. Check it in weather apps.

UV is stronger at high altitude, near the equator, and when reflected off snow, water and sand. You can burn on cloudy days.

How to protect your skin

Seek shade

Stay in the shade especially between 10 a.m. and 4 p.m. A simple rule: if your shadow is shorter than you, UV is strong.

Wear protective clothing

• long sleeves and pants made of tightly woven fabric
• clothing labeled with an ultraviolet protection factor (UPF) of 30 or higher
• a wide-brimmed hat (at least 3 inches) that shades the face, ears and neck
• wraparound sunglasses that block 99 to 100 percent of UVA and UVB

Use sunscreen correctly

Choosing sunscreen:

• broad-spectrum (protects against UVA and UVB)
• SPF 30 or higher. SPF 30 blocks about 97 percent of UVB. Higher numbers give a little more protection
• water-resistant (40 or 80 minutes) for swimming or sweating
• mineral (zinc oxide, titanium dioxide) or chemical filters both work. Mineral sunscreens are often better tolerated on sensitive skin and for children
• tinted mineral sunscreens also block visible light, helpful for melasma

Applying sunscreen:

• apply 15 minutes before going outside
• use about 1 ounce (a shot glass full) for the body of an adult, and about a nickel-sized amount for the face
• do not forget ears, neck, tops of feet, back of hands, scalp parting and lips (use SPF lip balm)
• reapply every 2 hours, and immediately after swimming, heavy sweating or towel drying
• check the expiry date
• sprays should be rubbed in and not inhaled. Do not spray directly on the face

Most people apply only a quarter to half the amount needed, which greatly reduces protection.

Avoid tanning beds

There is no safe tan. A tan is a sign of skin damage. Self-tanning products are a safer alternative, but they do not protect against UV.

Sun protection for babies and children

• under 6 months: keep out of direct sunlight. Use shade, clothing and a hat. If sun cannot be avoided, a small amount of sunscreen on exposed areas such as the face and backs of hands is acceptable
• over 6 months: use broad-spectrum SPF 30 or higher mineral sunscreen, plus clothing, hats and shade
• make sun protection a habit, as most sun exposure happens in childhood and adolescence

People who need extra protection

• fair skin, red or blond hair, freckles, light eyes
• many moles or atypical moles
• personal or family history of skin cancer (see dermatology surveillance)
• organ transplant recipients and others on immune-suppressing drugs
• people taking photosensitizing medicines, such as doxycycline, some diuretics, retinoids and certain NSAIDs (see photosensitivity)
• outdoor workers and athletes

People with darker skin can still burn and get skin cancer, though less often, so sun protection is recommended for everyone.

Sun protection and vitamin D

The body makes vitamin D in sunlight, but it is not necessary to risk sunburn to get enough. Vitamin D can come from food (fatty fish, fortified milk and cereals) and supplements. People who strictly avoid the sun may need a supplement. Ask your doctor.

Frequently asked questions

What SPF should I use?

Use a broad-spectrum sunscreen with an SPF of at least 30. SPF 30 blocks about 97 percent of UVB rays. Higher SPFs offer a little more protection. Applying enough and reapplying every 2 hours matter more than a very high SPF number.

How often should I reapply sunscreen?

Reapply every 2 hours when outdoors, and immediately after swimming, sweating heavily or towel drying. Water-resistant sunscreens last 40 or 80 minutes in water, as labeled on the bottle.

Is sunscreen safe for babies?

Babies under 6 months should be kept out of direct sun with shade and clothing. Small amounts of sunscreen can be used on exposed areas if needed. From 6 months, use a broad-spectrum mineral sunscreen with SPF 30 or higher.

Do I need sunscreen on cloudy days?

Yes. Up to 80 percent of UV rays can pass through clouds. Check the UV index, and use sun protection whenever it is 3 or higher, even if it is cloudy or cool.

Does wearing sunscreen cause vitamin D deficiency?

Studies show normal sunscreen use rarely causes vitamin D deficiency. If you avoid the sun strictly or are at risk, get vitamin D from foods or supplements rather than unprotected sun exposure.