Definition

It is an hypersensitivity reaction to a triggering agent that is normally harmless.

Accompanying signs & symptoms

Breathing difficulties, cough, wheezing, productions of mucus or phlegm in the airway, itchy eyes, nose or skin, skin rashes, blocked or running nose, sneezing...etc. 

Possible Causes

Over-reactions of the immune system to the triggering factor
Weak immune status

Physiological Mechanisms

From western perspective, allergies and hay fever are caused by over-reactive false immune responses and immune overreactions.

From integrative Chinese medicine perspective, such immune incompetence are the result of a weak body defence or in Chinese medical jargon, "Qi" deficiency. As our body defence act to protect us from viral and bacterial invasion, when our body defence is weakened, not only our body becomes vulnerable to colds and flu, it also fail to distinguish between real and false threats. Consequently, it triggers an over-reaction to factors such as temperature changes, dust mite and pollen.

Treatment Modalities

Chinese herbal medicine, Chinese herbal treatment for allergies

Mechanism of action of the herbs used

Chinese medicine treats allergies by doing the following:
Reducing the level of harmful hormones in the body which often suppress the normal immune response. 
Restoring the balance of hormonal regulation in the body 
Reducing the stress of the body
Regulating the distorted immune function
Activating the immune system
Promoting detoxification of the body
Improving one's energy, vitality and overall wellbeing

Health Advice

Reducing the intake of caffeine and cigarette smoking
Eat a balance diet
Establishing a regular eating habit
Encouraging moderate, regular and outdoor exercises

References

Longman concise medical dictionary, 1994

Chinese-English Manual of Common-Used in Traditional Chinese Medicine, Ou Ming, 1995