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Contact Dermatitis : Causes
   
Western Medicine Chinese Medicine

The disease occurs worldwide and affects both sexes and all age groups. It is common, occurring in up to four per cent of some populations. The range of potential sensitizing allergens is enormous, but a relatively small number of substances accounts for most cases. The most common examples are:

nickel (in costume jewelry and buckles)
 
chromate (in cement)
 
latex (in rubber gloves)
 
perfume (in cosmetics and air fresheners), and
 
plants (such as Primula or the Compositae).
 

Allergic contact dermatitis is mediated by T-cell hypersensitivity in the skin. Two phases of the disease are recognized:

Induction phase: This is the period during which a person is exposed to an initial allergen and the body's T-lymphocytes (cells of the immune system) respond and become sensitized.
Elicitation phase: When re-exposure to the same allergen occurs, the sensitized T-lymphocytes mount an increasing response and contact dermatitis results.

The induction phase can be as short as seven to 10 days after first skin contact, but it usually takes many months or years of exposure to small amounts of allergen to induce sensitization. Individual sensitivity varies according to the nature of the chemical, its concentration and the genetic susceptibility of the person exposed. Once sensitization occurs, it lasts for years, if not for life, and is generalized.

Re-exposure to the relevant allergen triggers the elicitation phase and produces dermatitis. Reactions can be elicited anywhere on the skin. In some instances systemic reactions have been provoked when the allergen enters the body by ingestion or injection.
 
The lungs and spleen have a powerful influence in contact dermatitis as they are the main organs that promote and support skin function. In TCM, skin and hair are the barriers of exogenous evils invasion, the protective qi that enhances its integrity is regulated by the lungs. Therefore skin diseases are always viewed as indicating a lung disharmony. The spleen is responsible for extracting nutrients from food and for transporting fluids throughout the body, and impaired function can contribute to unhealthy skin and swelling. In TCM, it is considered that contact dermatitis can be caused by both endogenous (originating from inside the body) and exogenous (originating from outside the body) factors.

Inborn susceptibility (endogenous causes)
The incidence of contact dermatitis is influenced by body constitution and is more likely to occur in individuals with a congenital/inherited predisposition to the disorder. In cases of congenital deficiency, the skin and tissues beneath are loosely bonded. This means that the protective qi is weak and that the body is more prone to a flare-up of fire evil or to the development of internal wind evil . Contact with certain substances, such as lacquer, drugs, plastic, rubber products, dyes or plants, facilitates transformation of heat evil internally in the body. The conflict between blood and qi against the heat evil triggers the skin disease.

Environmental pathogen invasion (exogenous causes)
In situations where external pathogens are allowed to invade the body directly, excessive fire evil will develop and accumulate. Circulation of blood and qi in the surface areas of the body becomes disturbed and does not flow smoothly. This in turn damages the integrity and function of the skin causing dermatitis.

Click here to see the causes of contact dermatitis from a TCM perspective