Asthma

Asthma is a type of airway obstruction characterized by a narrowing of the air passages in the lungs and caused by muscle spasm and mucus secretion.

The main symptoms of asthma are:

breathlessness,
wheezing, and
tightness in the chest.
During an asthma attack the bronchial tubes become partially obstructed making breathing difficult. Attacks may be triggered by:

allergens, such as pollen, dust and other pollution including cigarette smoke, fur or dandruff;
food allergies or intolerances, such as aspirin, food additives, yeast or moulds on foods;
deficiencies, such as selenium, and vitamin B6;
strenuous exercise;
temperature changes - especially sudden exposure to cold air; or
stress and anxiety.
What you can do to help

Try to remove the source of the allergen if this is possible. Keep dust and pollen levels under control and avoid possible ingested allergens.
Don't smoke and do avoid pollutants.
Eat a healthy diet that contains plenty of fresh fruits and vegetables. Onions are believed to have antiasthmatic properties and it is suggested that you have at least one cooked onion each day. It is best to avoid sugar and to eat a diet low in animal fats.
Vitamin C should be taken at 1g twice each day, for its antihistamine qualities.
Magnesium is thought to dilate the bronchial tubes, preventing a spasm and it also works to encourage a normal response to allergens. A daily supplement of 300 to 400 mg is suggested.
Vitamin B6, 50 to 100 mg per day, has been shown to reduce the number of asthma attacks in a group of patients.
B complex vitamins (10-20 mg per day).
Vitamin E 600 IU per day.
Antioxidants A (as beta-carotene) C and E as well as selenium should encourage recovery and prevent attacks.
The herb Ginko Biloba may also be beneficial.