Which sign should alert a mother that her child is experiencing an asthma attack?

Wheezing on expiration is a key indicator of an asthma attack, particularly in children. During an asthma attack, the airways become inflamed and constricted, leading to difficulty in breathing and the characteristic wheezing sound. This wheezing occurs primarily during expiration due to the narrowed airway, which causes turbulence in the airflow. While other symptoms may present during respiratory issues, wheezing specifically indicates that the airways are compromised and the child is struggling to breathe, making it a crucial sign for parents to recognize in order to seek prompt medical attention.

In contrast, the secretion of thin, copious mucus, a tight, productive cough, and a mildly elevated temperature are not definitive indicators of an asthma attack. Mucus production can occur in various respiratory conditions, not exclusively in asthma. A productive cough may suggest other issues, like an infection, rather than an asthma exacerbation. Lastly, a slightly elevated temperature, such as 99.4°F, could be the result of numerous benign factors and does not directly signify an acute asthma attack. Therefore, wheezing on expiration stands out as the most critical sign to alert a mother to a potential asthma attack in her child.