A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.
The skin and the mucous membranes which cover the openings of our bodies to the external environment (such as in the nose and mouth), form protective barriers which keep water inside the body, and keep the outside (filled with bacteria, fungi, dust, dirt, etc.) from coming in. The skin is really an organ of the body, and a large one at that. The skin is much more than just a simple covering, it is multi-layered, and underneath the surface (which is composed of dead cells), are other layers composed of living cells which react to irritants when they get through. When an irritant reaches these sensitive live skin cells, they can only respond in a limited number of ways, the first of which is a general response to any irritating chemical or physical agent (like sunlight); inflammation. Inflammation has four components; redness, pain, heat and swelling. The degree of inflammation is a direct result of the degree of chemical or physical irritation (dose-response). If the damage is great enough to cause cell death, then the response will be much more severe, and can result in areas of the skin becoming "denuded" (loss of the layers, with the deeper layers being exposed to the surface). Because the response of the skin to many different physical and chemical irritants is similar, the causes of skin irritation must usually be diagnosed by a physician who specializes in skin problems (a dermatologist).
This Toxicology Information Brief (TIB) describes one of the most common toxic affects produced by pesticides and other chemicals, cutaneous toxicity in its many forms. Cutaneous toxic reactions account for approximately 1/3 of all pesticide related occupational problems, however pesticides are not the only chemicals which can cause skin toxicity. For example, allergic dermatitis produced by poison oak is the most frequent cause of temporary disability in forestry workers. Dermatitis means literally "inflammation of the skin." Most often dermatitis is referred to as a skin "rash," however, this term is very non-specific. There are many different types of "rashes" and they differ quite a bit in the way they appear and in how they are produced.
Some of the more frequently encountered dermatitis problems in humans and food animals are primary irritant dermatitis and allergic contact dermatitis.
|Carrot||Castor Bean||Fig tree Sap|
|Some natural pyrethroides|
|Poison Oak||English Ivy||Pine|
|Poison Sumac||Tulip bulbs||Cashew|
|Tetradymia sp (Horsebrushes)||Phenothiazines|
|Tribulus terrestris (Goatshead)||Copper Toxicosis in Sheep|
|Hypericium sp. (St Johnswort)||Blue-green algae poisoning|
|Any condition that seriously damages the liver (pyrrolizidine alkaloid poisoning).|
Contact phototoxic photosensitization is the most common occupational phototoxic reaction in humans, and is caused primarily by plants. This type of toxic reaction occurs when the photoactive chemical produced by the plant (or fungus) contacts the skin, is absorbed into the skin, and then activated by sunlight. The result is the same as sunburn, and varies in intensity dependent on the amount of chemical exposure, and the amount of exposure to sunlight. Plants which cause it are listed in table 4.
|Mustard (with pink rot)||Klamath weed||Celery|
The symptoms are redness, pain, blistering and, following recovery, hyperpigmentation of the affected area. Historians record that the ancient Egyptians knew of this reaction and used it to darken light areas of the skin. Some forms of toxic chemicals from plants are still used today to treat hypopigmentation (abnormally light pigmentation of the skin).
The second type of photosensitization dermatitis is the photoallergic reaction. This disorder is very similar in appearance to allergic contact dermatitis; however, sunlight is required to initiate the process. It requires prior exposure to the chemical and sunlight, and is not very common.
Finding out just what has caused the dermatitis may involve "patch testing" in which the patient's skin is exposed to small patches containing dilute solutions of the suspect agents. In this way, the offending chemical can be identified and measures taken to prevent or minimize future exposure. The best way to prevent cutaneous toxicity is the appropriate and correct use of protective clothing, and the use of safe handling and application procedures.