Why do we get sick during colder weather?

When the temperature drops, your body goes through changes that may impact how it fights diseases and illnesses. When cold and dry air is breathed in, blood vessels in the respiratory system narrow to conserve heat, which makes it harder for white blood cells to move throughout the body to fight germs.

Viruses spread more easily in dry, winter air because there are fewer water molecules present to slow their movement. Heating your home in the winter also dries out the air. Nasal passages do not perform as efficiently in dry air, which can allow viruses to enter the body more easily.

Colder weather can also worsen preexisting conditions. Raynaud’s disease, which is the narrowing of blood vessels that supply blood to the skin, is aggravated by colder weather. People affected by arthritis will feel worse as restricted blood flow makes joints feel stiffer than normal. Colder air causes respiratory systems to work harder, exacerbating an ailment such as asthma or chronic obstructive pulmonary disease (COPD).

Contact your health care provider to work out a plan if you are concerned about your health as the weather turns colder, particularly if you have conditions intensified by cold.

Dr. Daniel Knight is a professor in the Department of Family and Preventive Medicine in the College of Medicine at the University of Arkansas for Medical Sciences.