Phytodermatitis Index

Reprinted with permission from the American Academy of Dermatology. All rights reserved. Please note that the slides are very large JPEG files that will take up to 6.5 minutes to view or download using a 28.8 kbps modem.

Mechanical Dermatitis

Cuts, abrasions and punctures in the skin caused by thorns, spines and hairy appendages of plants. These injuries can become secondarily infected with bacteria, mycobacteria or fungi.

Irritant Dermatitis

Reaction in the skin caused by irritating chemicals in the plant. These chemicals include acids, proteolytic enzymes and calcium oxide crystals. This is not an allergic reaction.

Phytophotodermatitis

Skin reactions are caused by furocoumarin chemicals in the plant and exposure to Ultraviolet A sunlight. Blisters form in a few hours after contact with the plant and sunlight. Hyperpigmented skin develops in the affected area when the blisters have healed and may last for months.

Allergic Contact Dermatitis

Allergic contact dermatitis requires previous sensitization to low molecular weight compounds in a plant. Not everyone develops an allergic reaction to these compounds. The most common plant causing this reaction is poison oak or ivy. The large family of plants, Compositae, contain chemicals called sesquiterpene lactones, which are sensitizers and irritants. Most of these rashes are chronic, eczematous rashes as compared to the severe blisters that develop from contact with the poison oak or ivy plants. Allergic contact dermatitis is the least common type of plant reaction except for problems with poison oak or ivy.

Contact Urticaria or Pharmacologic Injury

Urticaria (hives) develops after contact with the plant or plant material. The reaction can be allergic or non-allergic. In the non-allergic type reaction, irritant hairs on the surface of the plant enhance penetration of the pharmacological materials into the skin. These chemicals include acetylcholine, histamine and serotonin. The reaction can last for a few hours.

The allergic type reaction can result in swelling of the mucous membranes (eyes, lips and throat) with generalized urticaria. Individuals with atopic dermatitis are more prone to this type of reaction. Most of these reactions are caused by latex proteins, garlic, onions, tulips and lilies in susceptible people.

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