Side effects of drinking decaffeinated tea include headache, dizziness, itching and feeling faint. Decaffeinated tea undergoes a chemical treatment process during production that eliminates caffeine from the beverage. Some chemical treatments, such as carbon dioxide and ethyl acetate, change the flavor of the tea, while the process of methylene chloride treatment might produce adverse health reactions.
Regardless of treatment, most chemicals in decaffeinated tea occur in small amounts, posing little health risks. However, some people develop a sensitivity to the chemical methylene chloride. Only high and repeat exposure produces symptoms, primarily affecting the head and upper body. Although not affecting health, carbon dioxide and ethyl acetate treatments weaken teas and alter their flavors.