“…As a general practical principle cross-sensitization must be considered to be general within this family…” [That is, if one gives you a rash all the others will too.]

[First,] In previously unsensitized individuals, exposure is followed by a latent period of about nine to fourteen days before dermatitis appears.

In sensitized individuals, symptoms develop from a few hours to several days after contact, with itching at the sites of contact, usually the fingers, hands, forearms and legs. Papules appear, often in linear pattern, and soon evolve into vesicles or bullae. In severe cases the eyelids, other parts of the face, the genitalia and the trunk maybe affected. Except in regions well protected by hair, oedema may be considerable, and is particularly so in the eyelids and the male genitalia.

In most noxious species the allergen is widely distributed throughout the plant. Digging the soil in which roots are growing may cause dermatitis. The pollen and flowers of Toxicodendron are not allergenic [poison-oak depends on insect pollination; whereas mangoes rely on wind pollination and have irritating pollen] nor is smoke from the burning plant, unless the smoke contains incompletely burned plant material. [I’d have to disagree; smoke is evidence that combustion is incomplete, and firefighters have a lot of skin trouble.]

[Chronic plaques of thickened irritated skin develop in some individuals. Most commonly these are at sites of repeated exposure, often a wrist] In dermatitis constitutional symptoms are [un] usual, [except for fever, which occurs whenever the rash is extensive.

Some examples of  ANACARDIACEAE other than poison-oak  are the following:

Anacardium occidentale, the cashew nut tree:

A native of Brazil.

Unprocessed nuts are responsible for dermatitis amongst dock workers who unload them. Downing, JG (1940) “Dermatitis from Cashew-Nut Shell Oil” J. Indust. Hyg.  22 169. Museum has. 90% of these men kept working, and became more comfortable after three weeks; this is an example of “topical hardening”. On follow-up examination many of them had thick, cracked skin.

Improperly prepared cashews can cause acute gastroenteritis. Dark-colored cashews should be discarded.

Rengas or Renghas trees:

In the timber trade Rengas and Renghas refer to the heartwoods of ANACARDIACEAE of genera Gluta and Melanorrhoea. The hard durable wood of Melanorrhoea has also been sold as Singapore mahogany.

The heartwood of Gluta is blood red, with darker bands; it is hard, durable, easy to turn, and beautiful. However the sawdust irritates the mouth, nose and throat; and furniture made from it causes dermatitis. The sap slowly penetrates polish, even if the wood is seasoned. Two years of curing and a polyurethane lacquer finish are recommended. The woods are obtainable only on very special order, and the species have been inadequately collected, because of the irritancy of their saps.

One species of Gluta grows in Madagascar; the other twelve species are native to Indomalaysia. The twenty species of Melanorrhoea are from Southeast Asia, the Malay Peninsula and Borneo.

In Malaya acute rengas dermatitis with malaise and sometimes fever is not uncommon in estate laborers, gardeners and woodcutters. The fruit juice causes dermatitis; two companies of soldiers developed dermatitis after wading in water contaminated with their fruits. Occasionally a scantily clad person who scrambled through broken Rengas branches dies from the dermatitis.

Forestry workers are cautious working on these trees because the sap and sawdust causes blistering burns. Sometimes they anoint themselves with sesame oil, in an attempt to avoid the dermatitis. Also the felled trees may be left in the jungle for decay and white ants destroy the sapwood, before they are dragged out.

The three species of Lithraea are leading causes of dermatitis in South America. L. caustica is endemic to Central Chile from Coquimbo to Arauco, where it grows on hills and sunny plains. The lumber from this tree, Aroeira or litre, is used for furniture in Brazil and Chile; this furniture remains allergenic, and has sensitized 10% of the population in Southern Brazil. It is dangerous to sleep under the tree because of leaf exudates, especially in summer. The sap is caustic, and the dried wood is allergenic. [Lithrin is the name of the irritant in these plants.]

The forty species of  Mangifera, mango, are natives of Southeast Asia and Indo-Malaysia. Many species are now cultivated, or have become naturalized, in tropical regions around the world because of their importance as a source of food and timber. M. indica produce the grocery store mango.

In Hawaii during its fruiting season it is the leading cause of plant dermatitis. Unlike poison-oak mango pollen is irritant and allergenic; sniffing the blossoms provokes hard sneezing, and wind-blown pollen causes dermatitis. There are allergens in the fruit peel. Also stem sap gets on the peel during harvesting; the resulting spots appear black, bleached or varnished. Biting the unpeeled fruit causes rashes of the face around the mouth; rarely hives and shock occur.

Urticaria and anaphyllaxis are uncommon reactions other ANACARDIACEAE. However degranulation by urushiols is evidence that in many sensitive people there is an immediate component: Shelley, Walter B and Resnik, Sorrel S (1965) “Basophil Degranulation Induced by Oral Poison Ivy Antigen” Arch Dermat 92 August.

Mangoes are less sensitizing overall than the other sensitizing ANACARDIACEAE, and people growing up in areas where mangoes  grow are less easily sensitized to other ANACARDIACEA (Mitchell).

Mangoes are safe to eat and drink if contact with the peel and stem is avoided.

Metopium toxiferum, poison wood, is widely distributed in Florida and the Caribbean. The glossy leaves of young trees inspire transplantation to gardens, and use in wreaths and bouquets. In Florida the trees often grow so close to pine trees that they escape destruction when the land is cleared. The plant has caused dermatitis when branches brushed clothes on a clothesline.

R. coriaria is used for dying hides in Southern Europe. R. jugglandifolia is common in Costa Rica, where its local name, hinchador, means “the sweller”; this shrub is the right height to brush the face and hands. In Africa scratches and pricks from the sharp-tipped twigs of R. pyroides are extremely painful, and burn like fire; hence the name pyroides.