NEW YORK (Reuters Health) — A new study suggests that sun-filled family vacations can leave children with a permanent memento — more moles on their skin. These moles, also known as melanocytic nevi, are a precursor of melanoma, a deadly form of skin cancer.In a study of nearly 2,200 German children six to seven years old, investigators found that the more often a child’s family vacationed in sunny, southern climes, the more likely he or she was to have multiple melanocytic nevi. In contrast, there was no relationship between children’s moles and family vacations in northern European areas.

The findings suggest that occasional exposure to intense UV radiation is especially important in mole development, the study authors report in the American Journal of Epidemiology.

The findings suggest that parents should be vigilant in guarding their children’s skin during vacations in high-UV areas, according to the study authors, led by Dr. Olaf Gelfeller of the University of Erlangen-Nuremberg.

For their study, the researchers surveyed parents about family vacations taken since their child was born, as well as their child’s typical sun exposure throughout the summer. All of the children also had the number of moles on their skin counted.