Since mad cow disease turned up in the United States late last year, traced to a cow imported from Canada, federal regulators have issued rules to prevent the spread of the fatal disease, focusing on limiting beef imports, testing and other measures to protect the domestic herd.

Now, the Food and Drug Administration is addressing how the disease, formally known as bovine spongiform encephalopathy, might be transmitted through cosmetics, soaps, dietary supplements and certain food items, such as sausage casings.

The consuming public may not realize it, but a bovine is behind many beauty products and foods that might not be thought of as beef-based, such as candy, yogurt, cake mixes, mayonnaise and soups. The small intestine, for instance, is the only way to make some natural sausage casings.

So the FDA issued an interim rule in July that bans the use of domestic or imported "specified risk material," which includes the brain, skull, eyes, spinal cord and other organs from cattle 30 months or older, in many products under its jurisdiction. Also prohibited is use of the small intestine of all cattle, material from disabled cattle and from cattle not approved for human consumption. Records must be kept to certify that prohibited material didn't get into any of the products.

Some of these banned items are byproducts of slaughtering cattle and are important to the manufacture of soap, lotions, gelatin capsules and supplements.

"In all of these cases, it's a disease that is always fatal, and we don't know the infectious dose or the route of infection," said an FDA consumer safety officer, explaining the rationale for the rule. She said risk to the public is reduced if the FDA and the Department of Agriculture have a uniform policy on which bovine materials might be pathways to the disease. The FDA is reviewing comments on that rule.

Most of the affected manufacturers say the likelihood of the disease being transmitted though their products is infinitesimally small.

John Hathcock, vice president for scientific and international affairs of the Council for Responsible Nutrition, a trade group for the diet supplement industry, said supplement makers already avoid known sources of problem materials. Glucosamine chrondritin, used for arthritis, for instance, is highly processed and comes from the hoof, hide and bones of the animal, which are allowed under the rules.

Cosmetic manufacturers and makers of soap and detergent breathed a sigh of relief when the FDA exempted tallow derivatives and other kinds of tallow from the rule. The rule said tallow derivatives, such as fatty acids and glycerin, are the predominant cattle-related product used by the cosmetics industry. But manufacturers also use albumin, brain extract, brain lipid and other cattle-derived products.

What the FDA is trying to safeguard against, it said, is the application or ingestion of cosmetics made from prohibited parts, which may create a route for infection. It said it could cost the cosmetic industry up to $18 million to find alternatives for some of the ingredients it uses.

The Cosmetic, Toiletry, and Fragrance Association says it is unlikely the infection can be contracted from beauty products.

"This is someone with a wild imagination who wants zero risk," said Gerald N. McEwen Jr., vice president of science for the cosmetic trade group. "It isn't that easy to transmit that stuff. And find a product that has brain extract in it."

Sausage makers and the companies that supply their casings may be the hardest hit by the rule.

Under the rules at FDA and USDA, the small intestine, which is the material used to make natural sausage casings, is considered a risk material. Sausage makers are barred from importing, or acquiring domestically, intestines that were removed from cattle after Jan. 12, shortly after the diseased cow was discovered.

This means the makers of kielbasa, knockwurst, blood sausage, kishka and other Old World favorites are about to run out of casings -- even though the North American Natural Casing Association and its international counterpart have been pleading with regulators and the White House to change the rule.

The American Meat Institute, which represents meat and poultry processors, said the small intestine is a significant export product for slaughterers, especially to Japan. "For specialty sausage makers, it's a big item," said James H. Hodges, president of the group's research foundation. He said the one part of the small intestine that poses some risk of infection is routinely removed and discarded.

The prohibition has caused some sausage makers to stop production, share scarce casings with competitors, or find alternatives, according to Shirley A. Coffield, legal counsel for the North American Natural Casing Association. Hog and sheep casings are not the answer for bigger, heavier sausages like blood sausage.

"A lot of [makers] . . . want to remain consistent. Our membership prides itself on the traditional products," said Jay Wenther, assistant executive director of the American Association of Meat Processors, of Elizabethtown, Pa., which represents small processors.

Processors and casing makers want the FDA to limit removal to the one troublesome part or allow exports from BSE-free countries such as Brazil and Argentina.

"We are really, really upset," Coffield said. "We have $190 million worth of sausage in beef casings and thousands of companies are affected. If it's another year [of this], our people are out of business."