WASHINGTON (Reuters) – The U.S. Food and Drug Administration has delayed by six months rules on the marketing of sunscreen originally set to go into effect this summer, saying the extra time was needed to avoid supply shortages.

The FDA last year ordered sunscreen manufacturers to make a host of changes by June to sunscreen labels that would better explain how consumers should use the products.

After complaints from major trade associations that companies were having trouble making the changes, the agency late last week extended the deadline to December. Smaller companies have until December 2013.

“We’re thinking proactively here… we don’t want them to cease making sunscreens available this summer because they don’t think they’ll be able to meet the compliance date,” said Shelly Burgess, a spokeswoman for the agency.

The FDA had updated prior rules on sunscreen which dealt only with protection against ultraviolet B radiation but not ultraviolet A rays, which contribute to skin cancer and early skin aging. Sunburn is primarily caused by UVB radiation.

Now sunscreen makers would be required to pass a test by the agency to prove the product protects against both types of rays before labeling sunscreens as providing “Broad Spectrum” protection. Of those that pass, only sunscreens with a “sun protection factor” or SPF, of 15 or higher can claim to reduce the risk of skin cancer and early skin aging.

Sunscreen products that don’t pass the test or have passed but have an SPF between 2 to 14 can only claim to help prevent sunburn.

Under the new rules, manufacturers also cannot call their sunscreens “water proof” or “sweat proof,” but only say that they are water or sweat resistant.

Sunscreen makers also cannot claim to provide protection for more than two hours without reapplication or to provide “instant protection” without submitting data to prove that to the FDA.

Burgess said that some sunscreens with revised labels were already in the market but that the agency did not know how many.

(Reporting By Lily Kuo; Editing by Paul Thomasch and Eric Walsh)