TUESDAY, June 17 (HealthDay News) -- The U.S. Food and Drug Administration has sent letters warning more than two dozen companies to stop selling fraudulent products that claim to prevent or cure cancer.

The agency is also cautioning consumers not to buy or use these products, which include tablets, teas, tonics, black salves, and creams, and are sold under various names on the Internet.

"Health fraud has been around for years, and it is a cruel form of greed," David Elder, director of FDA's Office of Enforcement in the Office of Regulatory Affairs, said during a morning teleconference Tuesday. "Fraud involving cancer treatments can be especially heartbreaking."

The warning letters, sent to 23 U.S. companies and one Canadian and one Australian company, cover 125 unapproved products with labeling claims to cure, treat or prevent cancer. "These claims are unproven, unreliable, and they are unkind to the patient who is seeking help," Elder said.

Elder said the FDA is concerned that some of the products present a safety hazard to consumers. "Others can interfere with medicines that a patient has already taken. And they could be used to forgo medically acceptable treatment plans," he said.

The bogus cures include ingredients such as bloodroot, shark cartilage, coral calcium, cesium, ellagic acid, Cat's Claw, an herbal tea called Essiac, and mushrooms such as Agaricus Blazeii, Shitake, Maitake, and Reishi, the FDA said.

"These products pose either a direct health risk to consumers because the products themselves can cause harm, or a serious indirect health risk because the products are marketed for a serious disease, in this case cancer," Michael Levy, director of FDA's Division of New Drugs and Labeling Compliance in the Office of Compliance, said during the teleconference.

For example, so-called black salve products, touted to treat skin cancer, can be particularly hazardous, Levy said. "Black salve products essentially burn off layers of the skin and are supposed to also burn away skin cancer," he said. "But what we have seen is that it actually burns away healthy skin. There is documented evidence of black salve products destroying large parts of people's skin and the underlying tissue."

Levy also said the FDA is concerned that consumers will purchase these products instead of products that are proven to be safe and effective.

Elder said: "As a result of these warning letters, FDA expects prompt and complete corrective action. Firms that don't heed the warnings we have delivered, and other firms marketing similar unapproved products, may face further regulatory action from the agency."

According to the FDA, the fraudulent claims found on the products include:

• "Treats all forms of cancer."
• "Causes cancer cells to commit suicide!"
• "80% more effective than the world's number one cancer drug."
• "Skin cancers disappear."
• "Target cancer cells while leaving healthy cells alone."
• "Shrinks malignant tumors."
• "Avoid painful surgery, radiotherapy, chemotherapy, or other conventional treatments."

Companies that don't stop these violations can have their products seized or injunctions placed upon them and also are liable for criminal charges, according to the agency.

More information

For more on fake cancer cures, visit the U.S. Food and Drug Administration.