Protecting Babies from the Harmful Effects of the Sun
It is best to keep infants out of the sun completely, especially during the middle of the day when the sun's rays are the strongest and most harmful. If this is not possible, the baby should be covered appropriately, with long sleeved tops and long pants, a wide-brimmed hat or bonnet that shields the ears and neck from the sun, and sunglasses that provide protection against UVA and UVB rays. Hats and clothing should not be made of sheer fabric.
According to the American Academy of Pediatrics, sunscreen may be used in babies younger than 6 months, as long as it is applied in small areas. Combination sunscreen and insect repellent that contains DEET should not be used on children younger than 2 months of age.
Because an infant's built-in cooling system is not yet fully developed, babies are more sensitive to high temperatures and more vulnerable to dehydration. Make sure your baby doesn't get overheated and offer additional breast milk, formula or water in hot weather to help prevent dehydration. Watch for signs of heat-related illness, such as redness, fussiness, excessive crying and fewer wet diapers than usual.