This article is from the Asthma FAQ, by Patricia Wrean and Marie Goldenberg firstname.lastname@example.org with numerous contributions by others.
No, not all asthmatics wheeze. Although wheezing is extremely
common in asthmatics, in _All About Asthma_, Dr. Paul says,
"It is important to note that not all asthmatic symptoms need be
present for one to experience an asthma attack. For instance,
not all asthmatics wheeze. And sometimes wheezing is so slight,
it can only be heard with a stethoscope. With some asthmatics,
coughing is the only symptom present." Similarly, in _Children
with Asthma_, Dr. Plaut states that children with chronic coughs
"may have asthma even though no wheezing is present." He
diagnoses such children with asthma if their peak flow improves
when given an inhaled bronchodilator.