Hyoyeon revealed that she suffers severely from allergies.

She appeared on the June 18th broadcast of Mnet's 'GOOD GIRL' where she was together with her team members. Before going on stage, Hyoyeon started sneezing intensely, eliciting worry from her members. The reaction was so bad that Hyoyeon had to ask the staff for some time alone. 

Hyoyeon replied to the members' concerns by saying: "You guys are overreacting!" and admitted that she has allergies caused by temperature changes. She stated: "I am worried that I will not be able to perform well because of my allergies. It doesn't get better quickly after eating medicine." 

However, Hyoyeon aced her performance when it came time to perform.