Sunscreens provide a means of defending against the sun’s harmful rays, but the ingredients inside many of them pose some health risks. Making smart buying decisions can help adequately reduce the effects of UVA and UVB rays while avoiding exposure to harmful sunscreen ingredients.

A number of sunscreens on the market contain a host of harmful substances, which have been linked to reproductive and developmental issues in animals, as well as an increase in skin cancers in lab mice. Active ingredients such as titanium dioxide, zinc oxide and retinoids are some of the ingredients to watch out for on sunscreen labels.

According to a buying guide provided by Consumer Reports, a wide variability of effectiveness against UVA rays was found in a number of sunscreens tested. Out of the 20 sunscreens tested, 18 of them did not provide any protection against UVB rays as promised on the label. Seven of the products only tested “Fair” for UVA protection, and two of them actually tested “Poor.”

Experts suggest that when using sunscreen, it’s important to use an adequate amount to protect the skin against the sun’s rays, which is typically about two to three tablespoons. The product should ideally be applied 15 to 30 minutes prior to going outdoors, and should be reapplied every two hours, especially after sweating or swimming.

Spray sunscreens should be applied with great care, as the FDA is still analyzing the effects of inhaling these products.

Although using any sunscreen is better than using none when exposed to the sun, it’s best to look over the labels for harmful ingredients, and check the Ratings provided on ConsumerReports.org for products that tested “Good.”