Spotting Hidden Allergy Triggers, Like Dust Mites, Mold, and Pollen If you've been living with allergies, you probably know the obvious stuff by now -- don't take in stray cats, don't hang around in dusty attics, don't inhale deeply in smoking lounges. But that might not be enough. There could be hidden allergy triggers and irritants all around you that you don't know about.

"Hidden allergens and irritants are a huge problem for people with allergies," says Hugh H. Windom, MD, an associate clinical professor of immunology at the University of South Florida. "The environments we live and work in expose us to all sorts of things."

And these hidden allergy triggers aren't the only issue. Just as problematic are the unsuspected ways that you might be getting exposed -- even to allergens you think you're avoiding.

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To a person with allergies, the world can seem like a minefield. To help guide you through it, here's a rundown of some allergens and irritants you might be missing, along with advice from the experts on avoiding them.

Hidden Allergy Triggers and Irritants

• Indoor pollution. Every ragweed pollen season, you might dutifully shut the windows and barricade yourself in your home. But while you're focused on the allergens outdoors, you could be missing the equally troublesome irritants inside. Studies have shown that indoor air pollution is often at least twice as high as what you get outdoors -- and often much higher.
  
  "While there might be pollution outside, at least you have infinite ventilation," says Jay M. Portnoy, MD, president of the American College of Allergy, Asthma and Immunology (ACAAI.) "But inside, irritants can become very concentrated." So when you're looking for hidden allergy triggers, start inside. After all, that's where we spend 90% of our lives.
  
  
• Vacuum cleaners. Yes, vacuuming can actually be bad for allergies. A normal vacuum is fine for sucking up the obvious stuff, like dust, dirt, and pet hair. But the allergens themselves are so tiny that they can go right through the filter, rocketing out of the vacuum's exhaust. "Vacuuming with a low-efficiency vacuum is probably making things worse," says Portnoy. "You're turning your vacuum into an allergen dispersal device."
  
  What should you do? Much as we might all like to have a doctor-approved excuse for giving up on housework, that's not an option. People with allergies need to vacuum regularly, since a buildup of dust -- full of allergens like pollens, dust mites, and insect remains -- is the last thing you need.
  
  So instead, shell out for a vacuum with a HEPA (high efficiency particulate air) filter, which will be fine enough to catch most allergy-irritating particles. Another option is a central vacuum -- if your house has one installed -- since at least then the allergens aren't being dispersed in your living space, says Portnoy. Then, vacuum regularly -- especially if you have pets, or if you've had the windows open during pollen season.
  
  
• Cleaning products. Not only is vacuuming a problem, but many cleaning agents can be tough on people with allergies. While not proper allergens, cleaning agents can irritate the airways and trigger quite serious symptoms.
  
  The key is not to let the odors become too concentrated. "When you're cleaning in an enclosed space, you must always have good ventilation," says Pramod S. Kelkar, MD, chair of the American Academy of Allergy, Asthma, and Immunology's Cough Taskforce. "Always open the window or run an exhaust fan."
  
  
• Pets -- but not for the reasons you think. It's not just the animal dander. Even if you're not at all allergic to dander, pets are prime culprits for bringing hidden allergy triggers into the house.
  
  "Outdoor pets go outside and roll around in the grass, which could be covered in pollen or mold," says Portnoy. Then they come in and sit on the couch, and on your bed, and on you. The only solution is to either keep your pets indoors or bathe them regularly.
  
  
• Houseguests. Just like your pets, visitors can serve as a delivery system for hidden allergy triggers. They might bring in the allergens -- like cat dander -- on their clothes and bags and then leave them behind on the way out.
  
  "Even though they don't bring the cat itself, that indirect exposure can still cause significant allergic symptoms," Kelkar tells WebMD.
  
  Windom agrees. "There have been some amazing studies that found huge amounts of cat dander in places that cats have never been, like airplanes and schools," says Windom. "It just falls off everywhere."
  
  Treat your guests' belongings as warily as you would their cat. Ask guests to put their things in a closed room and then make sure you don't go in. Or you could even ask guests to leave their coats and bags in the garage. You might feel like a crummy host making demands, but you won't be much fun if you spend the whole visit sneezing anyway. Just explain the problem and any reasonable person should understand. If none of this works, try to meet your friends outside your home.
  
  
• Humidity -- too much or too little. As you probably know, moisture is a crucial ingredient for the growth of mold. Dust mites also thrive in a moist environment. So experts say that if you have allergies, you should try to keep humidity levels at 40% or below.
  
  But air that's too dry -- under 20% humidity -- isn't any good either. When the air is dry, the body's natural response is to moisturize it. In the process, Portnoy says, your nasal passages generate excess mucus and make you stuffed up.
  
  "People often blame dust in their heating vents for allergy symptoms in the fall and winter," Portnoy tells WebMD. "But I think it's more likely just the body's response to dry air."
  
  Here's a tip: get a hygrometer, a simple device that reads the humidity in your home. That way, you can either humidify or dehumidify, depending on the moisture levels.
  
  
• Electrical appliances -- especially your fancy air filter. You might have shelled out hundreds on a special ionizing air filter to protect your lungs. But it might be doing you more harm than good.
  
  "All electrical appliances, including air filters, generate ozone," says Jonathan A. Bernstein, MD, an allergist and professor of clinical medicine at the University of Cincinnati. Ozone is a gas that's a well-known irritant for people with allergies -- that's why people with asthma should stay inside on days with high ozone levels. But what's even worse is that many air cleaners deliberately churn out ozone as a means of freshening the air.
  
  "These devices are a big problem," says Bernstein. "Ozone can really be dangerous for people with asthma."
  
  
• Stoves and heaters. Combustion -- in gas stoves, fireplaces, kerosene lamps, and many other devices and appliances -- can produce nitrogen dioxide and other pollutants. If they're not vented to the outside, the gases they produce are coming directly into your living space. So, if possible, avoid using unvented appliances. Use fireplaces and wood stoves sparingly. And try not to rely on portable kerosene or unvented gas heaters at all.
  
  
• Furniture, rugs, and home improvements. If you're remodeling or redecorating,don't be surprised if your allergies act up. Many furnishings and construction materials contain formaldehyde and other volatile organic compounds (VOCs) that might irritate your airways. They include the glue used in carpet installation, the particleboard on your kitchen cabinets, the foam in your furniture, or the insulation in your walls, says Portnoy.
  
  Most of these irritants will fade over time, but it can take weeks or months. "If you can still smell it, it's definitely still a potential irritant," says Portnoy.
  
  If possible, start with prevention. Choose products that are less likely to cause symptoms. Go for real wood over particleboard, or at least seal the particleboard with a low-VOC sealant. Ask for carpets that are free of formaldehyde. Use low-VOC paints. If VOC-producing products are already in the house, try to limit your exposure. Ventilate the home as well as you can, so that the irritant doesn't become too concentrated.
  
  
• Your spouse's workplace. Yes, even someone else's on-the-job exposure to irritants can affect you. If someone in your family works at a factory, garage, or laboratory -- or anywhere else with chemical irritants -- he or she can bring them home. And that could start you sneezing and coughing. If possible, ask your spouse to change his or her clothing after work or immediately upon arriving home.
  
• Global warming. Many experts believe that climate change is making life worse for allergy sufferers. Global warming is associated with increased levels of carbon dioxide (CO2.) "Plants are happier as CO2 levels increase," says Portnoy. So what's the result? Some species of plants are thriving, and the length of their pollen season is getting longer.
  
  Portnoy says that the ragweed allergy season has been extended by almost a month over the last 10 or 15years. While it used to run from Aug. 15 to Oct. 1, Portnoy says that it's now dragging on from Aug. 1 through the middle of October. And that's not all. "There's also been an overall increase in ragweed pollen counts and the potency of the pollen," he says.
  
  Aside from doing your bit to slow climate change, there's not much you can do about this on your own. Just be aware that the pollen season might be coming sooner than you expect -- and be ready for it.