Excerpt from Botanical Dermatology

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Background

Plant-induced contact dermatitis is divided into 5 major categories. These include allergic sensitization, mechanical irritation, chemical irritation, contact urticaria (immunologic or toxin mediated), and photosensitization (see Phytophotodermatitis). Plant products cause a variety of adverse cutaneous effects, and they are responsible for most cases of allergic contact dermatitis. In the United States, most cases of allergic contact dermatitis are due to Toxicodendron plants.

This article provides a brief introduction to botanical dermatology and highlights the small minority of plants that cause skin reactions. This discussion of clinical manifestations and treatment options is a supplement to the material presented in Contact Dermatitis, Allergic.

Classification of plants

Taxonomy refers to the scientific description and organization of plants. Subsequent codification is outlined by the International Code of Botanical Nomenclature (ICBN) and maintained by a body called the International Association of Plant Taxonomy (IAPT).

The botanical binomial classification system provides every entity with 2 names: a generic designation and a specific epithet. The binomial name is traditionally followed by a reference to the person or authority who first reported that specific epithet. For example, the full binomial name of common poison ivy is Toxicodendron radicans (L.) O. Ktze. In this case, (L.) refers to Carl Linnaeus who issued the epithet radicans. O. Ktze is used in recognition of Otto Kuntze, who transferred the epithet radicans from the genus Rhus to the genus Toxicodendron.

Frequency

The risk of acquiring plant-related dermatitis is influenced by host susceptibility and exposure. Impairment in the barrier function of the skin may increase the propensity for sensitization. Chronically immersed hands (eg, florists' hands) may be particularly predisposed to plant-related dermatitis.

Allergic contact dermatitis requires exposure and sensitization to the causative plant products. In patch-testing conditions, more than 70% of the population in the United States reacts to poison ivy and poison oak allergens, whereas roughly 50% of the population has such reactions in nature.

Sex

Sex variations in the prevalence of sensitization to allergens reflect prior exposure and not innate differences in the sexes.

Toxicodendron-related dermatoses occur equally in both sexes. In the United States, ragweed dermatitis almost exclusively affects men. In Europe, dermatitis due to Primula species occurs predominantly in women. In India, Parthenium hysterophorus dermatitis (ie, scourge of India) affects men more often than women or children; the male-to-female ratio is 20:1.

Age

Allergic contact dermatitis due to poison ivy can occur in persons of any age, though infants and elderly individuals are reportedly less susceptible to poison ivy.

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