Oxygen is vital for all life processes and is a basic requirement of most of the living beings.
Oxygen is used in the normal body functions for oxidative reactions for energy supply.
Oxygen being highly reactive, produces in these oxidative reactions oxidants, otherwise known as free radicals.
Free radicals can oxidise and damage the body cells, cause oxidative stress and kill them.
An antioxidant is a molecule capable of slowing or preventing the oxidation of other molecules.
Our body produces a net work of metabolites and enzymes and also utilises the antioxidants consumed to counter these free radicals.
As these oxidants have a few useful functions like 'redox signalling', the body's antioxidant mechanism does not remove these free radicals completely, keeping them at a harmless optimum level.
When we are malnourished and our nutrients intake is not balanced, these check mechanisms for the free radical control go haywire starting chain reactions damaging and killing body cells.
Antioxidants check these chain reactions by themselves being oxidised.
Most of red, orange and yellow coloured fruits and vegetables, vitamins like A, C and E, green tea, spirulina, aloe vera, soya beans, date fruits, olive oil, vegetable oils, fish liver oils and minerals like selenium are very good sources of antioxidants.
Some of the uses of antioxidants are discussed below.

Asthma
Antioxidants are observed to reduce bronchial and lung damage from asthma.
Antioxidants also reduce narrowing of air tubes associated with asthma.
Asthma medication is found to be more effective when taken along with antioxidants. This decreases the need for higher doses.

Allergy
Antioxidants have been found to help in relieving allergy symptoms. By taking antioxidant rich foods allergy affected persons can get relief and the allergy may stop over a time.

Cataract
It is found that free radicals, by damaging the lens proteins of the eyes cause eye problems and cataract.
Consumption of antioxidant-rich foods such as carrots, citrus fruits, green leafy vegetables, spirulina and green tea prevents cataract growth and its complications.

Macular degeneration
In adults over 55 years of age macular degeneration is the main cause of blindness.
It has been found that antioxidants rich foods like vitamin A, C, E, carotenoids, zinc and selenium protect the retina and prevent the development of this condition.

Diabetes
Diabetes is a condition where in high levels of blood sugar are encountered with impaired metabolism resulting in decreased levels of insulin.
In a person with diabetes oxidative damages can give multiplying effect on the the damages already caused by diabetes.
A diet high in antioxidants is found to prevent further complications in diabetes.

Haemorrhoids
Haemorrhoids can cause painful or painless bleeding with bowl movement.
It is due to inflammation and swelling of blood vessels in the anus and rectum.
Antioxidants, specifically flavonoids are known to strengthen dilated veins.
It has been found that flavonoids help in maintaining and regaining structural integrity of the vessels.