The etiology and pathogenesis of vitiligo are rather complicated, and it may involve such a diverse array of factors as psycho-social factors, dietetic hygiene, living habit, regional and occupational factors, weather and seasonal changes. An understanding of the etiological factors and pathogenesis is very important for the prevention and treatment of the disease. In the recent years there is a gradual increase in the incidence of vitiligo, especially in children and adolescents. Our clinical observations demonstrated that the disease is closely related to environmental and food pollution, dietary habits and neuro-psychological factors.

1. Industrial pollution
The main source of environmental pollution is from industrial production. Other sources are exhaust fume by automotive vehicles, mining, used electric appliances and batteries. Many toxic substances released into the environment are harmful to the human body, such as sulfur dioxide, strong acid and base, lead, arsenic, mercury, benzene and phenol as well as heavy metals. Many of these substances can cause acute or chronic intoxication, directly or indirectly damaging the human tissue and organs. In recent years the destruction of the ozone layer has been proven by research to be caused by the increased production and release of Freon refrigerants into the atmosphere. The ozone layer can screen and decrease ultraviolet irradiation on the surface of the earth from the sun, and its destruction has led to increased UV irradiation on the surface of the earth and the resulting hazardous effects on the human body. All the above factors caused increased incidence in recent years of many skin diseases including vitiligo.

2. Agricultural pollution
The residual substances in the agricultural products and poultry from the over-use of chemicals in agricultural production, such as insecticides, disinfectants, ripeners and the growth hormones added in the poultry feed, are all harmful to the human body after consumption.

3. Pollution from house internal decoration
In recent years, many domestic and foreign reports pointed to a new source of pollution: house internal decoration. This has been called "the third pollution" or "in-house killer". Many of the decorating materials contained formaldehyde, ammonia, and benzene. Marble used for flooring contained radio-active substances. The substances can cause damage to the eyes, skin, nervous system, respiratory and digestive systems. In recent years national standards on decorating materials have been issued to standardize the house decoration industry.

4. Children's snack foods and drinks
The children's snack foods and drinks have obvious adverse influence on a child's development and health. The reasons are:
① the interruption of normal regularities of food intake. The children's snacks and drinks are often sweet and delicious, and can be taken by children as nibbles between regular meals. As the time passes the children's normal eating habit of regular meals will be interrupted.
② Damage to the stomach. The children's snacks and drinks are sweet. Traditional Chinese medicine holds that long-term intake of sweetened food will lead to indigestion due to "stomach heat", resulting in decreased appetite, even anorexia and dietary bias. Our clinical observations demonstrated that dietary bias and anorexia in children are often related to the use of snack foods and drinks. Therefore the long-term use of these snacks may lead to inadequate intake of nutrients, and influence a child's normal development, resulting in malnutrition and many illnesses.
③ Many snacks are not up to the standards and unhealthy. And they may also contain many chemical additives such as coloring, preservatives and sweeteners. Some of the swelling foods are processed in containers made of lead (e.g., pop-corn), and they are contaminated by heavy metal many times above the standards. These chemicals and heavy metal salts are directly hazardous to the child's body when taken overdose..
Researches showed that after absorption some of these toxic substances will inhibit the activities of certain enzymes and impair the melanin production. Some may directly damage the melanocytes. From the variations in the current incidence of vitiligo it can be observed that the incidence is higher in developing countries where the population density is high. The incidence of vitiligo is highest in India, with China, Japan and Southeast Asian countries next, and lower in the western developed countries. In our country the incidence of vitiligo is higher in various industrial cities, petroleum production regions and the coastal areas. Therefore environmental pollution and food contamination are one of the main causes for the development of vitiligo.

5. Endocrine and immunological dysfunctions
Certain pathogenic factors (chemical and heavy metal toxic substances) can damage organs and tissue, causing imbalance of the endocrine system and disturbances of immunological functions. The impaired immunological function is manifested by the production of anti-melanocyte autoantibodies which may cause vitiligo by destruction and depletion melanocytes from the epidermis, resulting in white patches. The pathogenic process is basically as follows: pathogenic factors → injury of melanocytes → release of antigens from the damaged melanocytes → stimulation of auto-antibody production from the body → immunological reaction between antigens and antibodies → destruction of more melanocytes → release of more antigens → production of more antibodies → more melanocyte destruction → large white depigmented patches. This is the reason why vitiligo with large white patches is more progressive. Human immunologic response is a complicated physiopathologic process (see appendix 2). The damaged melanocytes will release more antigens which will stimulate the production of more autoantibodies and the further destruction of melanocytes, and thus form a vicious cycle and further progression of the disease.
Apart from this, long-term psychological stress or trauma may also induce imbalance of the neuro-endocrine system. This is also an important factor for the initiation and development of vitiligo.

6. Deficiency of trace elements
Trace elements are active substances that participate in the body's metabolism. Some of these elements, such as copper, zinc, selenium and iodine, participate directly in the synthetic functions of melanocytes and have protective effects against the injuries by toxic substances. Research evidence has shown that the deficiency and imbalance of trace elements will result in malfunction of the melanocytes.

7. Genetic factors
It is a common misconception that all vitiligo cases are hereditary and some are worried that the disease will be passed on to the next generation. Our statistics from July 1 to December 31, 2000 showed that 38 of our 413 patients have positive family history, counting about 9%. Furthermore, for patients with positive history it does not mean that the disease in them is inheritable. Even if the disease is hereditary the therapeutic effects for patients with or without genetic factors are the same if early and proper treatments are given. The effectiveness is the same for patients with or without a positive family history. These patients can also be cured without recurrence. The patients and their family should not be worrying too much about this.

8. Trauma
Clinically white vitiliginous patches will sometimes occur after burning, scalding, stab or cut wounds, insect or mosquito bites, or infection. However, these traumatous injuries are only external factors and they induce vitiligo only on the basis of pre-existing in-coordination between yin and yang as well as between vital energy and the blood.

9. The theory of Traditional Chinese Medicine
The Chinese medicine holds that the development of vitiligo is the result of interaction of internal and external factors. The internal factors are the deficiencies of the liver, spleen and kidney, mainly the deficiency of kidney-blood, deficiencies of the kidney-yang and kidney-energy. These deficiencies result in the imbalance of the yin and yang of the body and the in-coordination between of vital energy and blood. On this basis wetness-heat and aversion to wind set in and the external harmful factors invade the body, causing the occlusion of channels and collaterals. The skin is therefore insufficiently nourished and deprived of nutrients, resulting in the loss of pigments and the formation of white vitiliginous patches. The traditional Chinese Medicine calls this condition baidian, baishi or baibofeng.
There is considerable similarities between the "imbalance between yin and yang", between "vital energy and blood" and "endocrine imbalance" and "immunological dysfunction" of modern medicine. It is our clinical experience that the mechanism of action of treatment of vitiligo by Chinese medicine is: adjustment of yin and yang, nourishing the liver and the kidney, supplementing qi and nourishing blood, expelling wind and removing dampness, clearing the channels and removing ecchymoses. Modern medical researches on Chinese medicines with immunological modulation effects have shown that some of these medicines have dual effects on the human immunological functions, that is they can enhance the immunological functions when the body immune response is low and can modulate the over-reactive immune response. We believe that the dual immunological modulation effects by Chinese medicines is the theoretical basis for the better therapeutic effects by Chinese medicines.

《Lesson Four：Prevention of vitiligo》>Lesson two <　>Back<