Dear Readers: Now that the days are getting longer and the sun will be out, we'll be spending more time outside with our pets. But that warm sun we've been waiting for all winter can be a mixed blessing.

Although a little sun is good for both you and your pet, too many ultraviolet rays can cause sunburn and eventually skin cancer. Excessive sun can also create problems for pets with existing skin conditions.

What can you do? Get some pet sunscreen, or use one made for babies (nothing containing zinc), and put some on the skin areas of your pet, like the tips of the ears and the nose. You can put it on the abdomen, too, but usually this is rubbed or licked off. Certain breeds and light-colored dogs and cats are most susceptible.

Skin cancer is one of the most common types of cancer in pets. Skin tumors are very common in older dogs, although they usually are benign. Cats are more likely to develop the more deadly kind, so be sure to have your pet examined by a veterinarian for any signs of abnormalities. Heloise

Dear Heloise: I am a new cat owner and was wondering how often to change the cat's litter box. What do your experts say?

A New Kitty Owner, via e-mail

Well, ask your cat! Solid waste should be cleaned up every day. The litter should be replaced when wet or you can smell it. Kitties like clean boxes, and sometimes they won't use them if they are too dirty. Would you want to? Heloise

Write to Heloise at P.O. Box 795000, San Antonio, TX 78279, or fax to 210-435-6473. E-mail heloise@compuserve.com.