What is contact dermatitis?
Contact dermatitis is a condition in which the skin becomes red, sore, or inflamed after direct contact with a substance. There are two types of contact dermatitis: irritant and allergic.
What is a patch test?
Patch testing is a diagnostic test that may determine which allergen is causing the skin to become irritated.
What is occupational dermatitis?
Occupational dermatitis is a skin disorder caused by coming into contact with certain substances in the workplace. It can have long term consequences for workers' health and in extreme cases it can hinder a person's ability to continue working. Research has indicated that 10 years after the condition first occurs, up to 50% of affected workers will still have some skin problems.
It has financial implications in terms of ongoing medical treatment, absence from work, social welfare compensation and possible civil claims. It brings other costs in terms of pain and suffering to affected workers. In many instances it may be totally preventable by simple inexpensive measures.
How many types of dermatitis are there?
There are 2 forms of contact dermatitis, irritant and allergic.
What is contact irritant dermatitis?
In contact irritant dermatitis, the substance that damages the skin is known as the irritant. A highly irritant substance is known as a corrosive. Irritant dermatitis makes up about 80% of contact dermatitis cases. The other 20% are allergic.
There are several causes of skin damage:
- Detergents, soaps (such as in repeated hand washing), or the use of solvents can remove the protective oily layer and so leave the skin exposed to damage.
- Physical damage such as friction and minor cuts can break down the protective layer and allow access to substances.
- Chemicals such as acids or alkalis can burn the skin layer.
Irritation is analogous to a chemical burn. It acts by eroding or burning the outer protective layers of the skin. Irritant contact dermatitis usually occurs only on the parts of the body that come in direct contact with the irritant substance e.g. hands, forearms, or face.
Common irritants are oils, solvents and degreasing agents which remove the skin's outer oily barrier layer and allow easy penetration of hazardous substances, alkalis and acids. Wet cement coming into contact with exposed feet and hands is an example of a skin irritant.
What is allergic contact dermatitis?
In this case, a substance causes a person to become sensitized or to develop an allergic reaction some time after initial contact. The type of allergic mechanism is known as Type IV or delayed hypersensitivity. People do not become allergic to a substance immediately at first contact. The sensitization period (the time between contact and the development of an allergy) can vary from a number of days to months or even years. The risk of becoming allergic depends on several factors:
- The nature of the substance. Substance with a higher likelihood to cause allergy is known as a skin sensitizer.
- The nature of contact. The higher or more repeated the exposure, the more likely it is for the individual to develop sensitization.
- The vulnerability of the host. Typically people with other allergies are NOT particularly more vulnerable to developing contact allergic dermatitis. Individuals with a previous history of non allergic dermatitis ARE more vulnerable. This may be because the sensitizer may more easily enter the bloodstream in those individuals.
Once the individual becomes sensitized, each time he/she comes into contact with the sensitizing substance, even in very small amounts, dermatitis will develop. This is different to irritant dermatitis which is dose related.
Sensitization is specific to one substance or to a group of substances that are chemically similar. Once sensitized, a person is likely to remain so for life. In allergic dermatitis the rash can occur in areas of the skin not in direct contact with the substance.
Common sensitizers are chromates (found in cement), nickel (cheap jewelry), epoxy resins, formaldehyde, wood dust, flour, printing plates, chemicals and adhesives.
*Source: Health & Safety Authority