Try this allergy test: Three little-known facts about indoor allergies

Bedding: If you've given up on down or feather bedding in favor of hypo-allergenic down alternative products, then you might be missing out. Dr. Nabeel Farooqui, an allergy and immunology specialist at Ohio State's Wexner Medical Center says it's usually not the down or feathers that are to blame.

"That material is washed thoroughly and stuffed inside very tightly-woven casings. Synthetic materials often have looser-weave casings which can allow more dust, mold and dander to collect. That's most often what people are allergic to -- not the feathers themselves," Farooqui said.

He recommends using the bedding material you find most comfortable, and wash it regularly in hot water to minimize dust and dander allergens. You can also try using dust mite covers on bedding.

Black mold: Mold spores are all around us and, while some people can be sensitive to high levels of mold, they generally do not cause serious health problems. According to the Centers for Disease Control, the type often described as 'toxic black mold' (stachybotrys chartarum) isn't actually toxic.

"This type of mold usually does not aerosolize and get breathed in because it's sticky from growing in a moist environment," Farooqui said. "There have been studies to examine the toxicity of this mold, but the evidence isn't there. However, molds commonly worsen asthma and allergy symptoms."

Farooqui says if you are sensitive to high levels of mold spores, avoid stirring up mulch, compost or decaying leaves when you're outside. When indoors, identify water leaks and other sources of moisture and get them repaired. Mold on hard surfaces can be cleaned away with a diluted bleach solution. Moldy absorbent materials like drywall, carpet or ceiling tiles need to be replaced.

Hypoallergenic pets: Animal lovers who find themselves allergic to four-legged family members might spring for a pure-bred poodle, Portuguese water dog, Bengal cat or other breed thought to be hypoallergenic, but Farooqui says don't expect allergy symptoms to go away completely.

"In short, completely hypoallergenic pets just don't exist," Farooqui said. "The fur isn't the problem. The allergens are in the pet's dander, which are derived from proteins in the skin, saliva and urine. We advise people to bathe their pet regularly to reduce dander. Keep the bedroom pet-free and use a HEPA air filter. If you're still having symptoms, talk to your doctor to see if you are a candidate for prescription medicine or allergy shots."

According to the Asthma and Allergy Foundation of America, about 40 million Americans report having at least one indoor/outdoor allergy and it can be hereditary. If one parent has an allergy, there is a 1 in 3 chance their child will have it. When both parents have the allergy, there is a 7 in 10 chance their child will too.

Farooqui says it's important to see a board-certified allergist to identify your specific allergy triggers and treat the symptoms properly -- because the allergy might not always be caused by what you think.