Poison ivy, allergens

Skin sensitizer May cause an allergic skin reaction 1 Warning Human evidence of skin sensitivity in a substantial number of persons or positive animal testing Pentadecylcatechol (poison ivy allergen), formaldehyde, epichlorohydrin, 2,4-dinitrochloro-benzene, nickel... 

As an allergen for testing purposes, synthetic 3-pentadecylcatechol is more useful than natural poison ivy extracts (of which it is one component). A stable crystalline solid, it is efficiently prepared in pure form from readily available starting materials. Outline a reasonable synthesis of this compound from 2,3-dimethoxybenzaldehyde and any necessary organic or inorganic reagents. 

Phenols occur widely throughout nature and also serve as intermediates in the industrial synthesis of products as diverse as adhesives and antiseptics. Phenol itself is a general disinfectant found in coal tar methyl salicylate is a flavoring agent found in oil of wintergreen and the urushiols are the allergenic constituents of poison oak and poison ivy. Note that the word phenol is the name both of the specific compound hydroxybenzene and of a class of compounds. 

Irritant contact dermatitis results from first-time exposures to irritating substances such as soaps, plants, cleaning solutions, or solvents. Allergic contact dermatitis occurs after an initial sensitivity and further exposure to allergenic substances, including poison ivy, latex, and certain types of metals. 

Allergenic plants causing skin eruption by contact include poison ivy (Rhus radicans L.), poison oak (Rhus toxicodendron L.), poison sumac (Rhus vernix L.), and stinging nettle (Urtica dioica L.). In the United States, poison ivy and poison oak cause nearly 2 million cases of skin poisoning and skin irritation annually, for a loss of 333,000 working days. In addition, these weeds cause 3.7 million days of restricted activity among those people who are susceptible to the toxins (1). 

The most frequent causes of allergic contact dermatitis in the United States include plants (poison ivy, poison oak, and poison sumac), metallic salts, organic dyes, plastic resins, rubber additives, and germicides.74 The most common skin patch test allergens found to be positive in patients along with potential sources of exposure are shown in Table 32.1.75 In patients with occupational contact dermatitis who were skin patch tested, the common allergens included carba mix, thiuram mix, formaldehyde, epoxy resin, and nickel.76... 

Hazard The toxic principle of poison ivy. Causes severe allergenic dermatitis. 

It is important to recognize that delayed chemical allergy can occur even some time afto" the chemical has been removed. Contact with poison ivy is a familiar example of an exposure that causes a delayed allergic reaction. Also, just as people vary widely in their susceptibility to sensitization by environmental allergens such as dust and poUen, individuals may also exhibit wide differences in their sensitivity to laboratory chemicals. Examples of substances that may cause allergic reactions in some individuals include diazomethane, dicyclohexylcarbodiimide, formaldehyde, various isocyanates, benzyUc and aUyUc halides, and certain phenol derivatives. 

The allergen may also be transferred from the fur of animals (who usually don t break out), from fomites [29] such as clothing or garden tools, or from one member of the family to another (connubial contact dermatitis or filial contact dermatitis) [31]. Poison-ivy oleoresin also can be carried on the fur of livestock. 

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