Representative Plants Causing Contact Dermatitis
Botanical name | Common name |
|---|---|
Amaryllidaceae | |
Narcissus species | Daffodil, Narcissus, Jonquil |
Anacardiaceae | |
See Table 7 | |
Annonaceae | |
Asimina triloba (L.) Dunal | Pawpaw |
Apocynaceae | |
Allamanda cathartica L. | Allamanda, Canario |
Nerium oleander L. | Oleander |
Araceae | |
See Table 5 | |
Araliaceae | |
Hedera canariensis Willd. | Algerian Ivy |
H. helix L. | English Ivy |
Aristolochiaceae | |
Aristolochia elegans M.T. Mast | Calico Flower |
A. gigantea Mart. & Zucc. non Hook. | |
A. grandiflora Swartz | Pelican Flower |
Asclepiadaceae | |
See Table 6 | |
Bignoniaceae | |
Campsis radicans (L.) Seem. | Trumpet Creeper |
Bromeliaceae | |
Ananas comosus (L.) Merrill | Pineapple |
Chenopodiaceae | |
Sarcobatus vermiculatus (Hook.) Torr. | Greasewood |
Commelinaceae | |
Rhoeo spathacea (Swartz) Stearn (= R. discolor (L’Her.) Hance) | Moses-in-a-Boat, Oyster Plant |
Setcreasea pallida Rose cv. ‘Purple Heart’ (= S. purpurea Boom) | Purple Queen |
Compositae (Asteraceae) | |
Ambrosia species | Ragweed |
Artemisia species | Mugwort |
Aster species | Aster, Daisy |
Chrysanthemum species | Chrysanthemum, Daisy, Feverfew, Marguerite |
Erigeron species | Fleabane |
Franseria acanthicarpa (Hook.) Coville (= Ambrosia acanthicarpa Hook.) | Poverty Weed |
Gaillardia species | Gaillardia |
Helenium autumnale L. | Sneezeweed |
H. microcephalum DC. | |
Iva species | Marsh Elder |
Lactuca sativa L. | Lettuce |
Oxytenia acerosa Nutt. (= Iva acerosa (Nutt.) R.C. Jackson) | Copper Weed |
Parthenium argentatum Gray | Guayule |
P. hysterophorus L. | Parthenium |
Rudbeckia hirta L. (=R. serotina Nutt.) | Black-eyed Susan |
Soliva pterosperma (Juss.) Less. | Spurweed |
Tanacetum vulgare L. | Tansy |
Tagetes minuta L. | Mexican Marigold |
Xanthium species | Cocklebur |
See Table 8 | |
Convolvulaceae | |
Dichondra repens J.R. & G. Forst. | |
Cornaceae | |
See Table 4 | |
Euphorbiaceae | |
Hura crepitans L. | Monkey Pistol, Sandbox Tree, Javillo |
Ricinus communis L. | Castor Bean, Higuereta, Ricino |
See Table 6 | |
Fumariaceae | |
Dicentra spectabilis (L.) Lem. | Bleeding Heart |
Ginkgoaceae | |
Ginkgo biloba L. | Ginkgo, Maidenhair Tree |
Gramineae (Poaceae) | |
Oryza sativa L. | Rice |
Panicum glutinosum Sw. | Sticky Grass |
Secale cereale L. | Rye |
Hydrophyllaceae | |
Phacelia campanularia Gray | California Bluebell |
P. crenulata Torr. ex S. Wats. | Scorpion Flower, Scorpion Weed |
P. minor (Harv.) Thell. ex F. Zimm. (= P. whitlavia A. Gray; Whitlavia grandiflora Harv.) | Wild Canterbury Bells |
P. parryi Torr. | |
P. viscida (Benth. ex Lindl.) Torr. | |
See Table 4 | |
Juglandaceae | |
Juglans nigra L. | Black Walnut |
Leguminosae (Fabaceae) | |
Prosopis glandulosa Torr. (= P. juliflora (Sw.) DC. var glandulosa (Torr.) Cockerell) | Mesquite |
See Table 4 | |
Liliaceae | |
Allium cepa L. | Onion, Cebolla |
A. sativum L. | Garlic, Ajo |
Hyacinthus species | Hyacinth |
Tulipa species | Tulip |
Loranthaceae | |
Phoradendron serotinum (Raf.) M.C. Johnst. (= P. flavescens (Pursh) Nutt.) | (American) Mistletoe |
Magnoliaceae | |
Magnolia grandiflora L. | Magnolia, Bull Bay |
Moraceae | |
Maclura pomifera (Raf.) C.K. Schneid. | Osage Orange |
See Table 8 | |
Myrtaceae | |
Eucalyptus globulus Labill. | Blue Gum, Eucalyptus |
Orchidaceae | |
Cypripedium species | Lady’s Slipper |
Palmae (Arecaceae) | |
See Table 5 | |
Pinaceae | |
Abies balsamea (L.) Mill. | Balsam Fir |
Primulaceae | |
Primula farinosa L. | Birdseye Primrose |
P. obconica Hance | Primula, German Primrose |
Proteaceae | |
Grevillea banksii R. Br. | Kahili Flower |
G. robusta A. Cunn. | Silk(y) Oak |
Ranunculaceae | |
See Table 6 | |
Rosaceae | |
Agrimonia species | Agrimony |
Rosa odorata (Andr.) Sweet | Tea Rose |
See Table 8 | |
Rutaceae | |
See Table 8 | |
Saxifragaceae | |
Hydrangea species | Hydrangea |
Solanaceae | |
Lycopersicon esculentum Mill. | Tomato |
Solanum carolinense L. | Horse Nettle |
S. tuberosum L. | Potato |
Thymelaeaceae | |
See Table 6 | |
Ulmaceae | |
Ulmus glabra Huds. | Wych Elm, Scotch Elm |
U. procera Salisb. | English Elm |
Umbelliferae (Apiaceae) | |
See Table 8 | |
Urticaceae | |
See Table 4 | |
Vitaceae | |
See Table 5 | |
Zygophyllaceae | |
Larrea tridentata (Sesse & Moc. ex DC.) Coville (= L. glutinosa Englem.) | Creosote Bush |
Representative Plants with External Irritant, Stinging Hairs, or Detachable Needles
Botanical name | Common name |
|---|---|
Cactaceae | |
Opuntia species (e.g., O. microdasys (Lehm.) Pfeiff.) | Bunny Ears, Prickly Pear |
Cannabaceae | |
Humulus lupulus L. | Hops |
Cornaceae | |
Cornus sanguinea L. | Bloodtwig Dogwood |
Euphorbiaceae | |
Acidoton urens Sw. | Mountain Cowitch |
Cnidoscolus chayamansa McVaugh | Chaya |
C. stimulosus (Michx.) Engelm. | Tread Softly, Bull Nettle |
C. texanus (Muell. Arg.) Small | |
C. urens (L.) Arth. (= Jatropha urens L.) | |
Dalechampia scandens L. | Spurgecreeper |
Platygyne hexandra (Jacq.) Muell. Arg. | Pringamosa |
Tragia volubilis L. | Pringamosa |
Hydrophyllaceae | |
Phacelia imbricata Greene | |
P. malvifolia Cham. | Stinging Phacelia |
Wigandia caracasana H.B.K. | |
W. urens (Ruiz & Pav.) H.B.K. | |
Leguminosae (Fabaceae) | |
Lupinus hirsutissimus Benth. | Stinging Lupine |
Mucuna deeringiana (Bort) Merrill | Velvet Bean |
(= Stizlobium deeringianum Bort) | Cowhage, Cowitch, Pica-Pica, |
M. pruriens DC. (= Stizlobium pruriens (L.) Medik.; Dolichos pruriens L.) | Pois Gratté, Vine Gungo Pea |
M. urens (L.) DC. | Bejuco Jairey, Ox-Eye Bean, Yeaux Bourrique, Torteza |
Malpighiaceae | |
Malpighia polytricha A. Juss. | Touch-Me-Not |
M. urens L. | Cowitch Cherry |
Sterculiaceae | |
Sterculia apetala (Jacq.) Karst. (in exposed fruit) | |
Urticaceae | |
Laportea aestuans (L.) Chew (= Fleurya aestuans (L.) Gaud.) | Pica-Pica |
L. canadensis (L.) Weddell | Wood Nettle |
Urera baccifera (L.) Weddell | Ortiga Brava |
Urtica dioica L. | Stinging Nettle |
U. urens L. | Stinging Nettle |
Representative Plants Containing Irritant Raphides
Botanical name | Common name |
|---|---|
Araceae | |
Alocasia species (e.g., A. macrorrhiza (L.) G. Don) | Elephant’s Ear, Taro |
Anthurium andreanum Linden | Flamingo Lily |
Arum italicum Mill. | Italian Arum |
A. maculatum L. | Cuckoopint |
Caladium bicolor (Ait.) Venten. | Caladium |
Calla palustris L. | Water Arum, Marsh Marigold |
Colocasia species (e.g., C. esculenta (L.) Schott | Elephant’s Ear |
Dieffenbachia species | Dumbcane |
Epipremnum aureum (Linden & André) Bunt. (= Pothos aureus Linden & André; Raphidophora aurea (Linden & André) | Pothos |
Birdsey; Scindapsus aureus (Linden & André) Engl. & K. Krause) | |
Philodendron scandens C. Koch & H. Sello ssp. oxycardium (Schott) Bunt | Heartleaf Philodendron. |
P. selloum C. Koch | |
Palmae (Arecaceae) | |
Caryota mitis Lour. | Fishtail Palm |
Vitaceae | |
Parthenocissus quinquefolia (L.) Planch. | Virginia Creeper |
P. triscuspidata (Siebold & Zucc.) Planch. | Boston Ivy |
Representative Plants Containing an Irritant Sap or Latex
Botanical name | Common name |
|---|---|
Agavaceae | |
Agave species (e.g., A. americana L.) | Century Plant, Maguey |
Apocynaceae | |
Acokanthera oblongifolia (Hochst.) Codd (= A. spectabilis (Sond.) Hook. f.) | Bushman’s Poison, Wintersweet |
Plumeria species | Frangipani |
Asclepiadaceae | |
Calotropis gigantea (L.) Ait. f. | Crown Flower |
C. procera (Ait.) Ait. f. | Algodón de Seda |
Euphorbiaceae | |
Euphorbia cotinifolia L. | Poison Spurge, Carrasco |
E. gymnonota Urb. | |
E. lactea Haw. | Candelabra Cactus |
E. lathyris L. | Caper Spurge, Mole Plant |
E. marginata Pursh | Snow-on-the-Mountain |
E. milii Ch. des Moulins | Crown-of-Thorns |
E. myrsinites L. | Creeping Spurge |
E. tirucalli L. | Pencil Cactus |
Excoecaria agallocha L. var. orthostichalus Muell. Arg. | Blinding Tree |
Grimmeodendron eglandulosum (A. Rich.) Urb. | Poison Bush |
Hippomane mancinella L. | Beach Apple, Manzanillo |
Pedilanthus tithymaloides (L.) Poit. | Slipper Flower |
Sapium hippomane G.F.W. Mey. | |
S. laurocerasus Desf. | Hinchahuevos |
Stillingia sylvatica Gard. | Queen’s Delight |
Synadenium grantii Hook. f. | African Milkbush |
Ranunculaceae | |
Caltha palustris L. | Pasque Flower |
Clematis species (e.g., C. virginiana L.) Pulsatilla patens | Marsh Marigold |
Mill. (= Anemone patens L.) | Virgin’s Bower |
Ranunculus species (e.g., R. acris L.) | Buttercup, Crowfoot |
Thymelaeaceae | |
Daphne mezereum L. | Daphne |
Dirca palustris L. | Leatherwood, Wicopy |
Anacardiaceae Producing Allergic Contact Dermatitis
Botanical name | Common name |
|---|---|
Anacardium occidentale L. | Cashew, Marañón |
Comocladia species (e.g., C. dodonaea (L.) Urban) | Guao |
Cotinus coggygria Scop. (= Rhus cotinus L.) | Smoke Tree |
Mangifera indica L. | Mango |
Metopium toxiferum (L.) Krug & Urban | Poisonwood, Cedro Prieto |
Schinus terebinthifolius Raddi | Brazilian Pepper Tree, Florida Holly |
Toxicodendron diversilobum (Torr. & A. Gray) Greene (= Rhus diversiloba Torr. & A. Gray) | Western Poison Oak |
T. pubescens P. Mill. (= T. toxicarium (Salisb.) Gillis; Rhus toxicodendron L.; R. quercifolia (Michx.) Steudel) | Poison Ivy |
Western Poison Ivy | |
Eastern Poison Oak | |
T. radicans (L.) Kuntze (=Rhus radicans L.) | |
T. rydbergii (Small) Greene | |
T. vernix (L.) Kuntze (= Rhus vernix L.) | Poison Sumac |
Representative Plants Producing Phytophotodermatitis
Botanical name | Common name |
|---|---|
Compositae (Asteraceae) | |
Achillea millefolium L. | Yarrow, Milfoil, Milenrama |
Anthemis cotula L. | Dog Fennel, Mayweed |
Moraceae | |
Ficus carica L. | Fig |
F. pumila L. | Creeping Fig, Creeping Rubber Plant |
Rosaceae | |
Agrimonia eupatoria L. | Agrimony |
Rutaceae | |
Citrus aurantiifolia (Christm.) Swingle | Lime |
Dictamnus albus L. | Gas Plant, Burning Bush |
Pelea anisata H. Mann | Mokihana |
Ruta graveolens L. | Rue, Ruda |
Umbelliferae (Apiaceae) | |
Ammi majus L. | Bishop’s Weed |
Anthriscus sylvestris (L.) Hofmann | |
Daucus carota L. var. carota | Queen Anne’s Lace, Wild Carrot |
Daucus carota var. sativus Hoffm. | Carrot |
Heracleum lanatum Michx. | Cow Parsnip |
H. mantegazzianum Sommier & Levier | Giant Hogweed, Wild Rhubarb |
H. sphondylium L. | Cow Parsnip |
Pastinaca sativa L. | Parsnip |
- 1.
Mechanical irritants
- 2.
Chemical irritants
- 3.
Allergens
- 4.
Phototoxins
- 5.
Pseudophytodermatitis
The majority of these complaints are managed by primary care physicians or dermatologists. This section provides a brief overview of the problem and should be supplemented by the use of a reference text or the advice of a dermatologist. Poison Control Centers, physicians, botanists, and medical toxicologists are frequently confronted by situations in which a plant is implicated in the formation of a rash, suggesting that the ability to recognize plant-induced dermatitis is important for all healthcare providers.
Mechanical injury is generally induced by plants with obvious physical characteristics that directly injure the skin, such as the barbs of aloe or the trichomes of stinging nettles (Urtica dioica L.) (Table 4). In the latter case, the stingers are fragile hypodermic syringe-like tubules that contain a mixture of irritant chemicals which are injected into the skin after the trichome breaks the dermal barrier. Following exposure, patients rapidly develop short-lived wheals with intense pruritus. Less-obvious exposures occur when the idioblasts found in common houseplants such as Dieffenbachia spp. injure the skin. These idioblasts contain both needle-like calcium oxalate crystals (mechanical irritants) in a soup of irritant chemicals (chemical irritants; Table 5). The crystals are injected into the skin or mucosa following mechanical stimulation of the idioblasts. Depending on the anatomical location of the crystal deposition, the clinical effects can be minor (e.g., skin), consequential (e.g., eye), or rarely lethal (e.g., airway). Treatment is generally supportive and symptomatic in nature. Skin involvement with a mechanical irritant should be treated with demulcent cremes, ice, and analgesics, and removal of the offending agent if appropriate. Ocular involvement is similarly managed with symptomatic care that generally includes ocular irrigation and systemic analgesics, and most exposures should prompt consultation with an ophthalmologist. Oropharyngeal exposures mandate rigorous attention to the airway, and patients may require corticosteroids to limit pharyngeal swelling. Endoscopy is often indicated in any patient with clinical findings consistent with consequential airway involvement (e.g., dysphonia, dysphagia, stridor).
Chemical irritants differ from the mechanical irritants in that they produce their clinical effects on the basis of a physicochemical quality of the toxin rather than through overt mechanical means (Table 6). Some of these toxins may be introduced along with mechanical irritants, as already noted with idioblasts. Chemical irritants may be directly irritating on the basis of pH or other chemical effects (e.g., solubility), mimicry of an endogenous compound (e.g., acetylcholine or histamine), enzymatic damage, or activation of inflammation. These agents may be protoxins that require metabolic transformation to produce the ultimate toxin (e.g., sinigrin in Brassicaceae (mustard) plants forms allylisothiocyanate). Chili peppers (Capsicum spp.) contain capsaicin, which induces the release of stored neurotransmitter (substance P) from sensory neurons and produces the deep aching pain characteristic of the “Hunan hand” syndrome, for example. Treatment of chemical-induced irritation includes decontamination by thorough washing of the affected area, analgesics, and symptomatic care.
Although any type of allergic response may occur, a type IV, or delayed, hypersensitivity response, also known as allergic contact dermatitis (ACD), is the most common form caused by plants (Table 7). Many occupations, such as florists, gardeners, and even outdoor workers uninvolved with plant work, are at risk for the development of ACD. Among florists, exposure to Peruvian lily, the very common centerpiece flower, results in ACD due to the common sensitizer tulipin A. The general pathogenesis of this reaction involves a primary exposure to a toxin resulting in an immune response (i.e., sensitization) developing in the affected individual. In some cases, particularly with toxins that are too small to elicit an immune response, the binding of the toxin or its metabolite to an endogenous compound (i.e., as a hapten) results in immunological recognition and the development of sensitization. Upon reexposure to the same or closely related toxin the primed immune system recognizes the antigen (or haptenized endogenous compound), and an immunological response is triggered. The result is a slowly developing (over hours to days) rash, consisting typically of pain, itch, redness, swelling, and blisters localized to the affected area. The sensitizing potential of the various plant-borne toxins varies, but urushiol, which causes “poison ivy”, is among the most potent and most frequently encountered sensitizers. Nearly everyone is capable of being sensitized to urushiol, accounting for the reason that “Rhus dermatitis” is given its own moniker. Although the reaction resembles irritant dermatitis, it is more slow to develop and requires previous exposure. Many related urushiol-like compounds from diverse sources [e.g., from mango (Mangifera indica) or cashew nut (Anacardium occidentale)] produce identical reactions in patients sensitized to urushiol.
Diagnosis includes the use of patch testing, in which a single or several known allergens are applied to the skin and a reaction is sought and is generally confirmatory. Although more advanced testing is available, this is a common initial screen for contact allergens. Occasionally, irritant dermatitis may result and be misinterpreted as ACD, so expert interpretation is needed. The risk of patch screening by this method is that sensitization to any of the tested compounds may occur just from the testing alone, so often the most strongly sensitizing plants are excluded from testing.
The primary therapy, of course, is avoidance of the known allergen. Because this is difficult or impossible in some situations, the use of barrier protection may provide a sufficient impediment to dermal exposure. Barriers include the use of clothing or of barrier creams that can be applied if an exposure is anticipated. Treatment of the ACD once it has occurred is generally symptomatic, with the use of analgesics, antipruritic medications (e.g., hydroxyzine, diphenhydramine), occasionally corticosteroids (generally topically applied), and rarely immune modulating agents (e.g., tacrolimus ointment). Desensitization may be attempted for patients with severe reactions or unavoidable exposures.
This is a relatively uncommon clinical entity, in which certain compounds increase the sensitivity of the skin (photodermatitis) to ultraviolet light (e.g., sunlight) (Table 8). Classically, psoralen, a furocoumarin derived from celery and other plants, enters the skin either directly by contact or via the systemic circulation following ingestion. In the skin, psoralen is activated by sunlight to produce oxidant skin damage, which manifests as burning, erythematous skin in sun-exposed areas, which may blister severely (i.e., sunburn). Psoralens may be administered therapeutically to patients with dermal disorders such as psoriasis to increase the sensitivity of the skin to therapeutic ultraviolet light.
Given the ubiquity of plants and the constant interaction of humans with plants, many dermatological disorders are often attributed to a contemporaneous plant exposure. However, mimics of plant dermatitis are common and may be missed due to the often simultaneous nature of the two exposures. For example, pesticides, fungicides, insects, and soil products may each induce dermatitis that is often indistinguishable from one of the aforementioned syndromes.
Without intense investigation or advanced medical testing, this link may be missed and the patient advised incorrectly to avoid a certain plant exposure. More consequentially, the patient may not be aware of the dermatitis trigger. The best method by which to distinguish pseudophytodermatitis from phytodermatitis is by having the necessary clinical suspicion and attentiveness to the exposure. Even then, this link is often difficult to make.
Enfield B, Brooks DE, Welch S, et al. Human plant exposures reported to a Regional (Southwestern) Poison Control Center over 8 years. J Med Toxicol. 2018;14(1):74–8. https://doi.org/10.1007/s13181-017-0643-3.
Sasseville D. Clinical patterns of phytodermatitis. Dermatol Clin. 2009;27(3):299–308–vi. https://doi.org/10.1016/j.det.2009.05.010.