WASHINGTON — More and more foods bear a mishmash of warnings that they might accidentally contain ingredients that could seriously sicken people with food allergies.

Yet there are signs that the labels are creating confusion among families that should heed them — even as new testing shows there is a real, if probably small, chance that foods with even the most vaguely worded warnings truly pose a risk.

The disconnect is sparking calls for standards on what are now voluntary warning labels. The Food and Drug Administration plans to seek advice from consumers and food makers, perhaps by year’s end, before considering whether to intervene.

Worried the labels may be losing credibility, the industry’s Grocery Manufacturers/Food Products Association already is preparing to update its own guidelines on when foods should carry the warnings.

Consumers see the label “on so many products, they say, ‘Oh heck, I’m going to ignore it,”’ laments Dr. Steve Taylor, a food scientist at the University of Nebraska who co-authored a recent study about the confusion.

For the seriously allergic, “I’ve characterized it as akin to playing Russian roulette with a really big gun that has 100 chambers and only one bullet. Sooner or later if you eat these products, you’re going to eat the wrong one,” he said.

About 12 million Americans have some degree of food allergy. Severe food allergies trigger 30,000 emergency room visits a year, and 150 to 200 deaths a year.

Food labels help the allergic avoid ingredients that could sicken them. A law that took effect last year requires foods that intentionally contain highly allergenic ingredients such as peanuts, shellfish or eggs to disclose that in plain language.

The accidental-allergy warnings are different: They’re aimed at foods that aren’t supposed to contain a particular allergen but might become contaminated with it. They may be made in the same factory, or on the same machines as allergen-containing goods.

In a report to Congress last year, FDA said a quarter of recently inspected food factories had the potential for such a mix-up.

The warnings are voluntary, so different companies use different, sometimes vague, wording. Nor does anyone count how many foods bear them, although all sides agree more are.

Enter the new research, in this month’s Journal of Allergy and Clinical Immunology.

First, the Food Allergy & Anaphylaxis Network, an influential consumer group, surveyed more than 600 parents of food-allergic children. In 2006, 75 percent said they would never buy a food with an accidental-allergy warning — down from 85 percent when the network posed the same question in 2003.

A warning’s wording determined if some parents ignored it: “May contain peanuts” sounds scarier than “packaged in a facility that processes peanuts” — and thus 88 percent said they heeded the first warning while just 64 percent heeded the latter.

That echoes an FDA experiment that found wording matters in persuading allergic consumers to believe the warning.

But are the warnings real? Nebraska’s Taylor tested 179 products that bore a variety of accidental-peanut warnings, and found 7 percent did contain peanuts — some of them traces, but some enough to seriously sicken.

That’s a small proportion. But Taylor is quick to note he only tested samples from two batches of each product. Test more — say the first batch of oatmeal cookies packaged after the machine was supposedly cleaned of peanut butter cookies — and that number may grow.

Moreover, contrary to some parents’ beliefs, peanuts were in some products with every version of the label, including two of 51 foods that bore a “may contain” warning and seven of 68 labeled “made in the same facility.”

On the other hand, the allergy network is increasingly concerned that foods that never before carried warnings suddenly are getting them — including puzzling ones, like canned vegetables with nut warnings — a trend perhaps fueling confusion.

“We’re seeing every week an increase in the number of these ’may contain’ statements on products you wouldn’t expect to see them on,” says network founder Anne Munoz-Furlong, whose group is pushing FDA and industry for new labeling standards.

“Don’t ignore it, because you don’t know when it’s true,” she tells consumers.

The industry is “troubled by what appears to be an increased use of ’may contain’ labeling,” says Regina Hildwine, labeling policy chief for the grocery manufacturers. “This is not just something that you should put on a package without thinking.”

Penny Ackerman of Bethlehem, Pa., is strict about label reading to protect her 3-year-old son, Gregory, who is severely allergic to peanuts and has a milder tree-nut allergy.

But, “we even have to watch labels we didn’t used to,” she says with frustration.

On a recent grocery trip, Ackerman didn’t notice until she got home that the chocolate chips she had always bought with confidence now warned they were made in a factory that uses peanuts. She wonders if the change is because of a new factory, or just that the company hadn’t gotten around to labeling until now.

“If you don’t see it on the label, is it safe or is it not safe? Because you don’t know.”

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EDITOR’S NOTE — Lauran Neergaard covers health and medical issues for The Associated Press in Washington.