But some people aren't too pleased with the effects of having the Douglas firs and Fraser firs around the house.

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That's because Christmas Tree Syndrome means sneezing and congestion for many people.

CTS is caused by molds found on Christmas trees that grow when the trees find warmth inside peoples' homes. The molds release spores that can cause allergic reactions and hay fever.

The allergic reactions are caused by pollens that collect in the tree's bark and when molds collect in the trunk and needles.

Artificial trees also have the potential to cause unwanted sneezing, especially if the tree has been stored since the previous winter season. Dust that accumulates disperses during assembly.

According to the Daily Mail, CTS was discovered in 2011 when allergy specialist Dr. Lawrence Kurlandsky conducted research at Upstate Medical University in New York to find out why respiratory illnesses peak around Christmas. Now, about 35 percent of people in the U.K. and the U.S. suffer from an increase of allergies and hay fever-like symptoms at Christmas.