Baby powder may not be so good for babies.

In fact, if you'll notice, it's rarely doctors who recommend its use.

The conventional wisdom that it cures or prevents diaper rash or prickly heat is of dubious substantiation, although it certainly does seem to make a tiny tush silky sweet.

Now, however, the prestigious medical journal Pediatrics has published a warning about some real baby powder hazards.

The article, written on the basis of six months of calls to a Long Island, N.Y., poison-control center, concludes that "to merely have a negative attitude towards these products is insufficient . . . the practice of using baby powders on young children should be actively condemned" until or unless changes are made in their packaging and labeling.

Two major manufacturers of baby powders, Johnson & Johnson and Pennwalt, which makes Caldesene, have defended the safety of their products. Caldesene does carry a warning on its cans to "keep this and all drugs out of the reach of children . . . "

However, Dr. Howard C. Mofenson, Dr. Joseph Greensher and colleagues at the Poison Control Center and department of Pediatrics of the Nassau County, N.Y., Medical Center, believe that "the true incidence of baby powder inhalation is grossly underestimated."

In the first 6 months of 1980, the Nassau center received 40 calls regarding children younger than 5 years who had inhaled baby powder.

The report in Pediatrics was based on follow-ups with 34 of the callers.

Only one of those children needed to be hospitalized, but the published report mentioned a more recent case of a child who had inhaled baby powder and, as a result, needed to spend several days on a respirator. Of the children in the study, most children were coughing and sneezing, but there was also vomiting in some others. Cyanosis (the condition produced by lack of oxygen in the blood) occurred in one case and "aspiration pneumonia" in another.

"Mothers should know that there's no proof that baby powder is essential," says Mofenson. Of the parents in the study, 24 said they used powder regularly on their babies; 10 were using it for a specific rash. In not a single case had powder been recommended by a doctor.

Another problem the researchers found was the similarity of many baby powder cans and disposable baby bottles. This, along with an infant's natural proclivity for putting things in their mouths, is "an invitation for trouble," says Mofenson.

Although most of the problems were relatively minor, "these are unnecessary consequences," says the report, "in light of the fact that there appears to be no medical indication for the use of these powders."

Even more ominous is the suggestion in the report that the powder, usually talc or zinc stearate, is related to asbestos, a known carcinogen when inhaled. In addition, when there is "medication" such as calcium undecylenate, a component of Caldesene and other medicated brands, the potential for toxicity is enhanced.

Cornstarch, which can be purchased either quite cheaply at the grocery store or more expensively perfumed and packaged for baby, is a possible alternative. But again Mofenson warns that "you don't want anything in a baby's airways." (He also notes that fungi, like the persistent monilia, have been known to grow in cornstarch.)

If a parent still insists on powder, Mofenson believes that they should:

Create a barrier so the baby cannot breathe in any powder.

Be absolutely certain the can is kept out of baby's reach. Watch out also for containers of foot powders and other talc-containing products.

Insist that manufacturers make containers with baby-proof closures.

Dr. Toby Litovitz of the National Capital Poison Center, at Georgetown University Medical Center, reports "a good number" of calls about powder inhalation, most without serious implications.

She adds a warning about youngsters eating flavored vitamins like "candy," especially those containing iron. "Some kids have eaten 80 to 100 pills at one sitting." There is potential, she says, for liver damage when iron is present.

National Capital Poison Center hotline: 625-3333. Montgomery and Prince George's counties are also served by the Maryland Poison Center, 800-492-2414. For other Maryland counties: 1-800-492-2414. Baltimore: 301-528-7701.