During an acute attack it is usually easy to make the diagnosis from the characteristic symptoms and signs. When the patient is referred for examination, symptoms may or may not be present. The diagnosis is then based on a detailed case history, physical examination, lung function, laboratory examination and in selected cases, a metacholine/histamine or exercise test. A daily recording of symptoms, lung function and of response to medication will help in the assessment of the reversibility of the disease and the effectiveness of treatment. Some of the important aspects of medical history are as follows:

(In adults)
In adults, allergic (extrinsic) asthma usually presents for the first time after excessive allergen exposure, while the onset of intrinsic (cryptogenic) asthma in many cases is related to an acute airways infection: "I have had asthma ever since I got the flu in  1996". Chronic asthma with late onset is seldom allergic.

Characteristics of the Asthmatic Attack
A typical episode of asthma starts with a vague sensation beneath the midsternal area and a feeling of chest tightness. Audible, musical wheezing develops, followed by dyspnoea, which is mainly expiratory. The acute asthma attack ends, usually after a few hours, with the expectoration of some very viscous sputum. The attack of dyspnoea is often accompanied or preceded by an irritating dry cough. When the disease is confined to the trachea and large bronchi, cough may be the only symptom, "dry asthma".

Provoking Factors
Asthma is exclusively confined to allergic exposure only in a few individuals (usually animal dander allergy), but in patients with recurrent or chronic asthma, allergens are only responsible in part for the symptoms. Increased  bronchial reactivity is clinically more important, as it makes the patient susceptible to daily insults, such as cold air, dust, irritating odours and fumes, tobacco smoke, excercise, forced respiration, laughing, and emotional stress. Patients often claim that they are "allergic" to these non-specific provoking factors. A full environmental history is important with particular interest being paid to the when and where of attacks.

Diurnal Variation
Periodic of attacks is a cardinal symptom of asthma. In addition, there is a typical diurnal variation in that many patients wake early in the morning with a tight chest, wheezing and dyspnoea, "morning dippers". These symptoms usually improve slowly during the forenoon, and in the afternoon the patient may be completely well and physically normal at the time of his out-patient visit.

Assessment of Severity
The severity of the disease must be determined once the diagnosis is made. It is important that both patient and family appreciate its likely effects on social life, working ability, family economy, and mental condition, as well as quality of life. It may be necessary, without frightening the patient, to inform him that asthma can be dangerous to life, if he does not adhere to the ordinated medication and advice given.

Some specific answers must be obtained in order to assess the severity of the condition. It is particularly important to know the number of restricted-activity days and work or school-loss days per month; in addition, how often the bronchial obstruction is severe enough to require a day to be spent in bed and a call for medical assistants. The number of attacks per day is difficult to evaluate in patients with persistent symptoms, but the number of disturbed nights due to asthma can usually be stated. The amount of inhaled medicine taken emergency calls and hospital admissions are also important parameters of  grading severity of asthma.