The clinical features of asthma exacerbations in early-onset and eosinophilic late-onset asthma may differ significantly.

Over 20 years ago, the concept of asthma control was created and appropriate measurement tools were developed and validated. Loss of asthma control can lead to an exacerbation. Years ago, the term "clinically significant asthma exacerbation" was introduced to define when a loss of control is severe enough to declare it an asthma exacerbation. This term is also used by health insurances to determine when an exacerbation is eligible for reimbursement of biologics in clinical practice, however, it sometimes becomes apparent that a clear separation between loss of "asthma control" and an exacerbation is not always possible. In this review, we attempt to justify why exacerbations in early allergic asthma and adult eosinophilic asthma can differ significantly and why this is important in clinical practice as well as when dealing with health insurers.