Allergy myths: Take this quiz for a reality check

Stress or emotions may bring on or worsen the symptoms of an allergy, but emotions don't cause allergies. An allergy occurs when your immune system overreacts to a substance (antigen) that's usually harmless, such as certain types of pollen, mold or pet dander. To repel these invaders, your immune system releases antibodies and inflammatory chemicals such as histamine and leukotrienes. If you have hay fever, a common respiratory allergy caused by pollens, these chemicals can inflame the linings of your nose, sinuses and eyes, causing sneezing, runny nose and watery eyes.

Though it's true that many allergies are only a nuisance, some are life-threatening. Allergies to foods such as peanuts and shellfish can trigger a potentially life-threatening allergic reaction called anaphylaxis, which causes constriction of your airways and a rapid decrease in blood pressure. Allergies to insect venom, latex and drugs such as penicillin also can trigger anaphylaxis. If you have a history of severe allergic reactions, your doctor may prescribe epinephrine, an injectable drug that you carry with you at all times. If you inject yourself with epinephrine at the beginning of such an allergic reaction, it can save your life by opening your airways and improving blood circulation.

Although allergies are unpredictable and can develop or go away at any age, childhood allergies often persist into adulthood. Most children don't outgrow hay fever and allergies to peanuts, tree nuts, fish or shellfish. However, most children do outgrow allergies to milk, eggs, soy and wheat. Most children with eczema, an allergic condition that causes swollen, reddened and itchy skin, improve by their teenage years. But they often have lifelong problems with dry, irritable skin that's sensitive to soap and cosmetics.

Decorative flowering plants don't typically cause pollen allergies. Trees, grasses and weeds such as red cedar, Bermuda grass and ragweed are the most common causes of pollen allergies. The male plants release tiny pollen grains that contain genetic material. Because the pollen is light and dry, it's carried by the wind to female plants. Along the way, it can easily end up in your respiratory tract and trigger sneezing and a runny nose.

Decorative flowering plants release pollen that is too large and sticky to be carried by the wind. Their pollen must be carried from the male plants to the female plants by birds and bees. So if a rose makes you sneeze, the cause is probably not its pollen but an irritating chemical in its scent.

Cottonwood is a hardwood tree found in North America. During the spring and summer, female trees release huge quantities of seed-containing "cotton," which floats through the air and sometimes blankets the ground. The cotton is highly flammable and can clog car radiators, swamp coolers and swimming pool heaters. But only rarely does it cause allergies. If you have watery eyes and a runny nose when the cotton is flying, the cause is much more likely to be other trees or grasses that are pollinating at the same time. And, by the way, this "cotton" is not the same as the cotton used in fabrics.

Even in the driest regions, trees, grasses and weeds produce potentially allergy-inducing pollen. The desert is home to such allergy-producing species as mesquite trees, sage and witch grass. Ironically, newcomers to the desert who are seeking to escape allergies often bring plants with them that cause allergies. Though not native to the desert climate, plants such as Bermuda grass and olive trees succeed because desert communities pipe in enough water from far-away rivers and reservoirs to allow for year-round watering. Moving to the desert may relieve your allergies for a few months. But you're likely to develop allergies to new substances within a few years.

Milk, eggs and peanuts cause the vast majority of allergic reactions in children. Peanuts, fish, shellfish, and tree nuts such as walnuts, almonds and cashews are the main offenders in adults. Only rarely do commonly blamed foods such as strawberries and tomatoes cause allergies.

Milk allergy is much more common in children than in adults. If you experience bloating, cramping, nausea, gas or diarrhea after consuming a dairy product, the problem is probably not allergy. It's likely lactose intolerance, a nonallergic condition that makes it difficult to digest the sugar in milk.

It's not an animal's hair that causes allergies, so the length of hair doesn't matter. A Chihuahua is just as likely to trigger allergies as is an Old English sheepdog. That's because most pets produce allergenic skin flakes (dander), saliva, urine and skin oils.

Intentional exposure to a substance you're allergic to won't increase your tolerance for it or eliminate your allergy. It only makes your allergy symptoms worse. Avoid purposely spending free time with your cat if you have a pet allergy, filling your house with allergenic plants if you have hay fever, or strolling the lawn after mowing has stirred up mold spores if you have a mold allergy. And indulging in peanut butter when you have a known peanut allergy is dangerous because it increases your risk of life-threatening anaphylaxis. Allergen immunotherapy, a type of controlled exposure to allergens, is the only safe and effective type of allergen exposure that can improve allergies.