Sunburn is a visible reaction of the skin's exposure to ultraviolet (UV) radiation, the invisible rays that are part of sunlight. Ultraviolet rays can also cause invisible damage to the skin.

Excessive and/or multiple sunburns cause premature aging of the skin and lead to skin cancer. Skin cancer is the most common type of cancer in the US and exposure to the sun is the leading cause of skin cancer.

“Children often spend a good part of their day playing outdoors in the sun, especially during the summer,” says Dr. Lauren LaGrega, Pediatrician at the Harvard Vanguard Medical Associates Cambridge practice. “Children who have fair skin, moles, or freckles, or who have a family history of skin cancer, are more likely to develop skin cancer in later years,” she adds.

Exposure to the sun during daily activities and play causes the most sun damage. Overexposure to sunlight before age 18 is most damaging to the skin.

UV rays are strongest during summer months when the sun is directly overhead (normally between 10:00 a.m. and 3:00 p.m.).

First aid for sunburn includes the following:

• Have your child take a cool bath or use cool compresses on the sunburned area.
• Give your child acetaminophen or ibuprofen for discomfort. Be sure to follow the directions on the container.
• Apply a topical moisturizer, aloe gel, hydrocortisone cream, or a topical pain reliever to sunburned skin. Avoid commercial products that contain Benadryl or benzocaine, because of the possibility of skin irritation or allergy.
• If blisters are present, do not break them open, as infection can occur.
• Keep your child out of the sun until the burn is healed.

Specific treatment for sunburn will be determined by your child's pediatrician and may depend on the severity of the sunburn. In general, call your child's pediatrician if the sunburn is severe or forms blisters, or if your child has symptoms of heat stress such as fever, chills, nausea, vomiting, or feeling faint.

“Protection from the sun should start at birth and continue throughout your child's life,” says Dr. LaGrega. It is estimated that 60 to 80 percent of total lifetime sun exposure occurs in the first 18 years of life.

The best way to prevent sunburn in children over 6 months of age is to follow the A, B, Cs recommended by the American Academy of Dermatology:

• Away: Stay away from the sun in the middle of the day. This is when the sun's rays are the most damaging.
• Block: Block the sun's rays using a SPF 15 or higher sunscreen. Apply the lotion 30 minutes before going outside and reapply it often during the day. Sunscreens should be used sparingly in infants under 6 months of age when exposure to sun is unavoidable.
• Cover-up: Cover up using protective clothing, such as a long sleeve shirt and hat when in the sun. Use clothing with a tight weave to keep out as much sunlight as possible. Keep babies less than 6 months old out of direct sunlight at all times. Hats with brims are important.