(CNN) The US Food and Drug Administration issued a warning to consumers Wednesday to stop using over-the-counter teething products that contain benzocaine.

It also sent letters to manufacturers asking them to stop selling the teething products.

Parents might use these products to temporarily relieve a child's teething pain, but the agency said they pose a "serious risk" to infants and children and often are not effective, since they can wash out of the mouth quickly.

The danger the products pose could come in the form of methemoglobinemia , a condition in which the oxygen level in blood dips dangerously low; it can be fatal. Symptoms include rapid heart rate, lightheadedness, difficulty breathing, sleepiness, headache, skin that is pale and nails that are blue or gray. The symptoms can start minutes after a product is used or up to one to two hours later. Babies who experience these problems should get medical attention immediately.

The FDA said that if companies that make these products do not stop selling them, it will take regulatory action to get the products out of stores.

"Because of the lack of efficacy for teething and the serious safety concerns we've seen with over-the-counter benzocaine oral health products, the FDA is taking steps to stop use of these products in young children and raise awareness of the risks associated with other uses of benzocaine oral health products," FDA Commissioner Dr. Scott Gottlieb said in a statement. "The FDA is committed to protecting the American public from products that pose serious safety risks, especially those with no demonstrated benefit."

The FDA will also require that prescription local anesthetics for teething children update their product box warnings to let parents know that they too may lead to methemoglobinemia.

Benzocaine products are sold as gels, sprays, ointments, solutions and lozenges under brand names Anbesol, Baby Orajel, Cepacol, Chloraseptic, Hurricaine, Orabase, Orajel and Topex and as store brands and generics. Those marketed to adults can stay on the market but may need new label information.

Church & Dwight Co., which sells and markets Orajel products for teething, said in a statement that the safety of its customers and their children is its highest priority, and it is immediately discontinuing the distribution and sale of Orajel teething products containing benzocaine. That includes Orajel Medicated Teething Gel, Orajel Medicated Nighttime Teething Gel, Orajel Medicated Daytime & Nighttime Teething Twin Pack and Orajel Medicated Teething Swabs.

"In addition, we also are revising the Drug Facts Label on all over-the-counter oral health care products that contain benzocaine with an intended use other than teething to emphasize that these products should not be used for teething pain or in children under 2 years of age," the statement said. "In addition, we are adding warning statements to more clearly identify the risks and symptoms presented by methemoglobinemia, a rare but serious condition associated with the use of benzocaine."

This is not the first warning about benzocaine from the FDA. In 2011, the agency warned consumers about the methemoglobinemia potential of the products. At the time, it estimated that there have been more than 400 cases of benzocaine-associated methemoglobinemia reported to the FDA or published in medical literature since 1971. There are probably additional cases that weren't documented.

It's also not the first teething product that the FDA has cautioned against. In September 2016 , the agency warned parents not to use homeopathic teething tablets and gels.

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The American Academy of Pediatrics has told parents to use alternatives such as hard rubber teething products and to avoid frozen teething toys, as they can injure a baby's mouth and cause more pain . It suggests that parents can rub their babies' gums to give them temporary relief.

Dr. Lisa Thebner, a New York-based pediatrician, said parents still ask about the products with some frequency.

"It often has the word 'baby' in the title, so parents will naturally reach for the product," she said. "I will often address it when they ask, or I'll try to address it during the well-baby checkups. I have, for a while, cautioned against topical gels because of the danger, and babies are in the population at the highest risk for harm, and if you look at the risk versus benefit, it's not even all that helpful. Rubbing their gum or giving them something hard, like a teething ring, it will be a much bigger help."