And our noses seem to beg us for pleasant aromas all year long. But if you think that air fresheners and scented candles are a safe alternative to the natural scents of your Thanksgiving meal, think again. A presentation at the Annual Scientific Meeting of the American College of Allergy, Asthma & Immunology (ACAAI) revealed that breathing in air fresheners can cause a number of health problems — such as headaches and breathing difficulties — especially for those who already suffer from allergies or asthma.

The presenter, Stanley Fineman, M.D., president-elect of ACAAI and associate clinical professor in the department of pediatrics at the Emory University School of Medicine, cited a 2009 study in the Journal of Environment Health, which found that 20% of the general population, 34% of asthmatics and 58% of people with chemical sensitivity reported health problems.

So what causes this reaction in certain people? A study from the Natural Resources Defense Council (NRDC) found that some air fresheners contain phthalates, “hazardous chemicals known to cause hormonal abnormalities, birth defects and reproductive problems.” The NRDC tested 14 common air fresheners, none of which listed phthalates as an ingredient, and found that 86% of the products tested contained these chemicals. This included products that advertised themselves as “all natural” or “unscented.”

Likewise, scented candles can produce soot, lead, organic compounds and volatile organic compounds. According to a Master of Science in Public Health thesis by J. David Krause, Department of Environmental and Occupational Health: “Scented candle usage indoors may cause high levels of respirable soot, with risks to occupants for both acute and chronic health effects.”

(Speaking of candles, check out this HellaWella story on fire safety.)

If you find yourself needlessly suffering, ditch the air fresheners and make sure your home has good ventilation — open windows or use fans to maintain air circulation.