Hay fever, runny noses and other allergies are among the most common maladies sending people to the doctor or drugstore.

More than 26 million Americans have allergic reactions, primarily to pollen, food and medications, and they spend more than $500 million a year on treatment.Yet allergies are poorly understood by the public and often improperly diagnosed and treated by physicians, according to experts in the field.

Serious problems affecting consumers and potential solutions were revealed at the American College of Allergy and Immunology's annual meeting last month in Los Angeles. Here are some of them:

-Food allergies are overdiagnosed by doctors relying solely on medical history or unreliable tests, said Dr. Sami L. Bahna, chairman of allergy and immunology at the Cleveland Clinic Foundation.

Ear, nose and throat specialists (otolaryngologists) believe that food allergies affect 19 percent of all people, or 1 out of 5, according to a survey of 700 doctors. But allergists and immunologists estimate that only 8 percent of the population, or 1 out of 12, have food allergies.

"I cannot imagine that one out of every five people has allergies to food. This is not feasible," Bahna said.

Allergists generally confirm a diagnosis by making sure that patients have observable reactions to specific foods, rather than relying on skin or lab tests, Bahna said.

Chronic runny or stuffy nose is often misdiagnosed and poorly treated by doctors who overlook non-allergic causes, such as physical obstruction, medication reactions and tumors, said Dr. Bryan Spofford, director of a Denver research institute.

Doctors should examine nasal passages and sinuses with a scope and X-rays to rule out other causes before prescribing long-term treatment with shots or sprays, Spofford said.

-Skin tests are not effective for determining whether headaches are caused by food allergies, said Dr. John Condemi of the University of Rochester.

Patients should get a list of foods that can trigger headaches and see if they have problems after eating particular items, he said.

Foods containing histamines, including beer and chocolate; nitrates, including hot dogs and packaged meats; and alcohol can trigger headaches.

People who drink four cups or more a day of coffee, tea or cola drinks can get headaches from caffeine withdrawl between servings, Condemi said. Reducing or eliminating caffeine consumption is one solution.

-Asthmatics can save money and avoid trips to the emergency room by using a portable machine that delivers prescription drugs for asthma attacks.

Emergency room visits were cut by more than half, and hospitilization was cut by two-thirds in a study of 33 children up to age 12 who used a home nebulizer machine, said Dr. Jay Portnoy of the University of Missouri in Kansas City. The device consists of a mask covering the mouth and nose that delivers a drug in aerosol form. It costs about $150, or about the same as one emergency room visit.

Home nebulizers, which reduce early inflammatory reactions in the lungs, provide the same treatment given in emergency rooms. The devices are particularly useful for younger patients who can't use a metered dose inhaler, Portnoy said.

In his discussion of food allergies, the Cleveland Clinic's Bahna said these allergies are difficult to diagnose because common symptoms can be caused by a variety of illnesses.

The most common food allergy symptoms in adults are hives, often accompanied by severe itching or swelling of the face; gastrointestinal problems such as diarrhea; and respiratory difficulties such as wheezing. Seafood, nuts and eggs most often cause allergic reactions, Bahna said. Cow's milk is the most common allergen in infants and children, he said.

Making the wrong diagnosis may prevent the patient from being treated for serious non-allergic diseases that can cause similar symptoms, he said.

Doctors can mistakenly blame foods if they rely only on what patients tell them or use unreliable tests, he said. Blood tests (RAST) and skin-scratch tests can be used for screening, but they must be confirmed because they are only about 60 percent accurate, Bahna said.

Tests using drops under the tongue (sublingual testing), cytotoxic testing (blood-cell reactions to allergens) and injection of food extracts into or under the skin have not been shown to be reliable, Bahna said. "If we base the diagnosis on medical history alone, patients could have a difficult life or suffer from malnutrition for no reason," he said.

Suspected food allergies should always be confirmed with elimination-challenge testing. This involves showing that symptoms improve when a specific food is eliminated from the diet and recur when the patient eats it, Bahna said.

Tests should be blinded, which means that the patient should not know whether he is consuming the suspected food or a placebo, he said.

Doctors should rely on symptoms that they can observe, such as skin reactions, vomiting, wheezing or severe pain, rather than subjective feelings such as fatigue that generally can't be verified, Bahna said.

Using strict criteria, Bahna estimated that only 2 percent to 5 percent of people have real food allergies, and most of them have problems with only one to three foods.

Once a food allergy is diagnosed, the best treatment is avoidance. Shots are not effective against food allergies, he said.

Chronic runny or stuffy nose is easily misdiagnosed because doctors often assume that allergies are to blame and ignore four other major causes, said Denver res earcher Spofford. Symptoms can result from a deviated septum (cartilage blocking the nasal passage )or enlarged adenoids, which may require surgery. Nasal passages can be swollen by a reaction to birth control pills, estrogen during pregnancy or menopause, some high blood pressure medications and abuse of decongestant sprays, Spofford said.

Most decongestant sprays are highly addictive and can cause chronic stuffy noses if used for longer than three days.

Doctors also need to rule out sinus blockages resulting from scar tissue, fractured facial bones or tumors, and reactions to smog or toxic fumes.

When patients have runny or stuffy noses all year long, they should have a scope examination and X-rays for about $65 before receiving shots costing hundreds ofdollars. These diagnostic tests are under-used because many allergists have not been trained to do them, Spofford said.

It's not enough to simply treat allergies when patients also have narrowed or blocked nasal passages that make symptoms worse, he said.

"If you have a badly deviated septum and one nasal passage is too narrow, you are very miserable when you have a cold or allergy because the passage can become blocked," Spofford said.