I am not sure if sunscreen harms animals, but not wearing it puts people at high risk for developing skin cancer.  Sun is very strong these days, and all of us should exercise caution when having fun in the sun.  Here are the basic rules of sun safety:

First, do not stay in the sun, seek protection of shade as much as possible.  

Second, avoid being in the sun between 10 a.m. and 4 pm.m. when the sun is the strongest.  

Third, wear sunscreen SPF at least 30 and reapply it every 2 hours and after each swimming.


Suggested readings:

Fun in the sun

http://www.pluggedinparents.com/index.php?option=com_content&task=view&id=203&Itemid=0

The ABC of skin cancer

http://www.pluggedinparents.com/index.php?option=com_content&task=view&id=240&Itemid=0

UV detector

http://www.pluggedinparents.com/index.php?option=com_content&task=view&id=565&Itemid=0

Best regards.