Asthma also called bronchial asthma, occurs when the airways in your lungs (bronchial tubes) become inflamed and constricted. The muscles of the bronchial walls tighten, and your airways produce extra mucus that blocks your airways. Signs and symptoms of asthma range from minor wheezing, cough, difficult exercising, shortness of breath, chest tightness to life-threatening asthma attacks, needing ventilatory support.

Causes
It isn't clear why some people get asthma and others don't, but it's probably due to a combination of environmental and genetic (inherited) factors.

Asthma triggers are different from person to person. Exposure to various allergens and irritants can trigger signs and symptoms of asthma, including:

Airborne allergens, such as pollen, animal dander, mold, cockroaches and dust mites
Respiratory infections, such as the common cold
Physical activity (exercise-induced asthma)
Cold air
Air pollutants and irritants such as smoke
Certain medications, including beta blockers, aspirin and other nonsteroidal anti-inflammatory drugs
Strong emotions and stress
Sulfites, preservatives added to some perishable foods
Gastroesophageal reflux disease (GERD), a condition in which stomach acids back up into your throat
Menstrual cycle in some women
Allergic reactions to foods such as peanuts or shellfish

Diagnostic tests -
1. Bedside clinical exam by a physician to determine wheezing/whistling sounds, however wheezing can occur in several other conditions too
2. Measurement of lung function by spirometry or pulmonary function tests

Treatment -

Inhaled corticosteroids - These medications reduce airway inflammation and are the most commonly used long-term asthma medication. Unlike oral corticosteroids, these medications are considered relatively low risk for long-term corticosteroid side effects. You may need to use these medications for several days to weeks before they reach their maximum benefit.

Long-acting beta-2 agonists. These inhaled medications, called long-acting bronchodilators, open the airways and reduce inflammation. They are often used to treat persistent asthma in combination with inhaled corticosteroids. Long-acting bronchodilators should not be used for quick relief of asthma symptoms.

Leukotriene modifiers reduce inflammation and decreasing mucus production.
Cromolyn and nedocromil - thought to decrease allergic reactions
Theophylline, a daily pill that opens your airways (bronchodilator) along with increase contraction of your respiratory muscles, helping breathing.

Quick-relief medications
Also called rescue medications, you use quick-relief medications as needed for rapid, short-term relief of symptoms during an asthma attack, or before exercise, if your doctor recommends it.

Short-acting beta-2 agonists, such as albuterol. These inhaled medications, called bronchodilators, ease breathing by temporarily relaxing airway muscles. They act within minutes, and effects last four to six hours.

Ipratropium - Your doctor might prescribe this inhaled anticholinergic for the immediate relief of your symptoms. Like other bronchodilators, ipratropium relaxes the airways, making it easier to breathe. Ipratropium is mostly used for emphysema and chronic bronchitis.

Oral and intravenous corticosteroids to treat acute asthma attacks or very severe asthma. Examples include prednisone and methylprednisolone. These medications relieve airway inflammation. They may cause serious side effects when used long term, so they're only used to treat severe asthma symptoms.

Medications for allergy-induced asthma. These decrease your body's sensitivity to a particular allergen or prevent your immune system from reacting to allergens. Allergy treatments for asthma include:

Immunotherapy. Allergy-desensitization shots (immunotherapy). Over time, they gradually reduce your immune system reaction to specific allergens.

Anti-IgE monoclonal antibodies. This medication reduces your immune system's reaction to allergens.

Ref: Mayo Clinic, Emedicine, Chest (Journal of the ACCP)