Contact Dermatitis in the Garden

by Cynthia W. Mueller, Galveston County Master Gardener

It's summertime now, and gardeners are more liable to experience contact dermatitis in the landscape. Instead of just walking past plants, scratching a little here and there with the hoe, moving the hose around, or carefully picking or cutting parts of plants, gardeners are 'toiling' outside to hoe vigorously, trim or rip out plants and carry them away by the armloads to the compost or trash pile under the sweltering summer sun - while perspiring and getting scratched and scraped by leaves and woody vegetation. Often, arms and legs are bare at this time, giving much more direct contact. These more strenuous activities under different conditions may bring on a whole range of contact dermatitis symptoms, depending on the plants involved. Almost every gardener has had the experience of blundering into poison ivy or poison oak by mistake, but when these plants are not present, many folks are not aware of the source of their discomfort, itching, permanent darkening of the skin, or blisters, until after the fact. The face and especially the eyes are often most susceptible.

Angelica officinalis
Angelica officinalis

Some of these skin problems are short-lasting, and are triggered by the small hairs on vegetables such as corn still in the husk, stacked up on the bare arm and inside of the elbow, or by touching the stalks and leaves of okra while picking. These effects may be annoying but subside quickly with no lasting after-effects.

Euphorbia family members such as poinsettias, 'Mexican poinsettia' (Euphorbia heterophylla) and the familiar pencil cactus (Euphorbia milii) (not really a cactus at all) ' have milky sap that will cause burning or reddening of the skin after extensive skin exposure. It's important to remember that the strength of contact dermatitis reactions depend in part on the susceptible nature of the individual.

The Composite family, as typlified by chrysanthemums and sunflowers, has a number of offenders that cause dermatitis at the time plants are handled. While certainly annoying to the majority of people, these symptoms are usually not long-lasting, although sometimes florist workers become so sensitized that they must wear gloves.

The Umbellifera (or Carrot) family has a number of more serious garden offenders, such as angelica, commonly called 'Wild Celery' (Angelica archangelica), Chinese Angelica (Angelica sinensis and a number of other closely related species, called 'Dong Quai' in Chinese). These Chinese angelicas are ingredients in many herbal remedies. Herb growers are finding that plants of angelica are easier to obtain than in the past, and because it's a striking-looking herb with a history of many uses, have included it in the garden. Angelica is one of the flavor ingredients of such drinks as absinthe, chartreuse, vermouth, Benedictine, and Dubonnet. The stems and roots are an old fashioned favorite for candying. But if a gardener is wrestling with big angelica plants in the heated sun, a severe skin reaction with blistering may result. Its roots contain both psoralen and furancoumarins, which are able to permeate to the DNA of the skin layers and create changes that can cause hypo- or hyperpigmentation, some of which may be almost permanent. If the sap gets into the eyes, serious problems may result. A well-grown plant may grow to six feet in height and needs to be pruned back on occasion. At this time caution should be used while touching the leaves and stalks.

Angelica at the US Botanic Garden
Angelica at the US Botanic Garden

Even garden celery and its close relative Lovage (also members of the Carrot or Umbellifera family) are capable of causing allergic reactions. Celery, dill, parsley and parsnips are also from the same family and are capable of causing rashes, while too much exposure to seeds of the ornamental Bishop's Weed (Ammi majus) is capable of actually creating permanently darkened skin areas.

Some dermatitis symptoms can be seasonal in nature. Gardeners handling bulbs and loose skins of such bulbs as tulips, daffodils, narcissus and hyacinth may complain of itching and burning of the skin at planting time. Among workers in Holland who routinely handle or harvest bulbs over a period of time, as many as 75% may show symptoms of occupational dermatitis with fissured, dry, hyperkartotic skin, and may have to resort to daily wearing of gloves.

Other plants that cause occupational dermatitis among harvesters or even grocery store workers may include alstroemeria flowers, English ivy, artichokes, and asparagus. But these symptoms are usually passing and do not cause any permanent damage.

Another herb found in Texas gardens is rue (Ruta graveolens). Rue has been grown for its medicinal qualities for hundreds of years, and still to this day is often be seen in Mexican American yards. A popular horticultural variety with an especially blue/silver coloration is called 'Jackman's Blue.' It's good to use caution when trimming back or cleaning up this perennial. Do not let the sap touch your skin, especially if working in the sunshine, as blistering may result.

After contact with suspect plants it's a good idea to wash the areas thoroughly with soap and water, apply sunscreen and stay out of the sunshine for at least 48 hours. Because ultraviolet light can pass through window glass it's a good idea to stay away from windows, too.

Gardeners in semi- or tropical areas that have developed any allergies to cashews should be careful of handling mango plants or biting into the fruits, especially if the skins are still on. Allergies to natural rubber gloves can 'cross' into contact dermatitis with fig trees or even Schefflera plants kept indoors.

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