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Vegetation, vegetables, vesicles: Plants and skin

Posted on: Thursday, 3 July 2003, 06:00 CDT

FRANCES NORTHALL discusses how apparently innocuous plants can sometimes cause severe skin conditions

Plants and plant extracts can adversely affect the skin in several ways that can be all too familiar, but sometimes surprising. Skin effects are most commonly localised and result from direct plant contact, but there are some instances where plant consumption can affect the skin and others where skin contact can lead to systemic effects.

Plants are generally considered harmless or even beneficial to the skin and there are certainly many available skincare products containing plant extracts. These plantenhanced products can involve native or exotic species, and may claim almost miraculous properties with the potential to make skin younger, less wrinkled and more toned, thereby tending to promote the idea that plants are unlikely to cause skin problems.

PLANT 'STINGS'

Stinging nettles may be the plant most people in the UK associate with skin discomfort and are probably most children's introduction to the less pleasant side of plants, competing with brussel sprouts in the unpopularity stakes!

The scientific name for stinging nettles, Urtica dioica, leaves no doubt as to the origin of the term 'urticaria' to describe the skin reaction they cause. Brushing against a nettle is equivalent to being injected with many very small hypodermic syringes. The plants are covered with tiny, hollow, rigid hairs each with a minute sac at its base containing an irritant liquid. This liquid is squeezed out as the hairs are flattened by the hapless human (Lovell 1993, Bombardelli and Morazzoni 1997).

Nettle 'stings' cause a burning sensation, erythema and swelling with maximum intensity between three and five minutes post-contact, followed by pruritus. The visible effects and the burning, itching sensation usually fade within one or two hours. A tingling paraesthesia may persist for up to 12 hours (Oliver et al 1991) or occasionally 36 hours or more. It is unclear how the injected fluid acts, but the immediate effects have been attributed to its histamine content (Kulze and Greaves 1988, Oliver et al 1991).

It is unlikely that anyone would present in an emergency department after an encounter with a nettle patch, but if they do there are various suggestions for treatment. Vigorous massaging of the affected area or application of cold compresses may reduce symptoms (Lovell 1993). The beneficial effect attributed to rubbing dock leaves, from the Rumex species, on nettle stings is probably due to the rubbing rather than properties of the leaves themselves. Bathing in tepid water may also provide some relief from nettle stings (Cooper and Johnson 1998).

PHYTOPHOTOTOXICITY

One of the more dramatic, uncomfortable and persistent plant-and- skin conditions is phytophototoxicity. This can occur from skin contact with plants containing chemicals known as psoralens followed by exposure of the area to ultraviolet light. Psoralens sensitise the skin to sunlight and the phototoxic effects are due to ultraviolet-induced binding of these chemicals to nuclear DNA and subseguent cell death. Resultant skin damage can be severe (Lown and Sim 1978, Song andTapley 1979).

Phytophototoxicity is characterised by the development of erythema, oedema and burn-like lesions within 24 hours and possibly large, fluid filled blisters within 48. Affected skin can be very itchy and painful. The effects subside within a few days, but there may be residual brown pigmentation and scarring which can persist for several months. Affected areas may remain hypersensitive to ultraviolet light for many years (Gunby 1980, Lovell 1993, Cooper and Johnson 1998).

The plant best known for this phytophototoxicity phenomenon is probably giant hogweed (Heracleum mantegazzianum). This giant plant, a native of south west Asia, became popular in larger gardens for its 'architectural merit'. Now widely naturalised, it can be found along the banks of rivers and canals, and on damp roadsides. Rue (Ruta graveolens) is also well known to cause phytophototoxicity (Table 1).

Toxicity may result from any activity that involves bruising, cutting, damaging or touching the foliage in combination with exposure to ultraviolet light. The use of strimmers without adequate protective clothing is a well documented means of exposure as multiple small fragments of plant material and sap are thrown up at operators' exposed skin (Freeman et al 1984, Reynolds et al 1991). The resultant effect is known as 'strimmer's rash'.

In cases of skin contact with minimal or no damage to the plant, moisture such as dew or perspiration can be a factor in the phytophototoxic reaction (Sommer and Jillson 1967, Gunby 1980).

Many cases of phytophototoxicity are described in the literature. In one example two people used strimmers to clear plant undergrowth, including H. mantegazzianum. It was a sunny day and they took off their shirts. Twelve to 24 hours after strimming they both developed a macropapular rash with bright red irregular papules over the anterior chest wall and arms. The rash persisted for between two and three days, and subsided leaving hyperpigmented areas (Reynolds etal 1990).

In another example a 27-year-old man attended hospital with dermal lesions similar to partial thickness burns four days after harvesting H. mantegazzianum in the sun. Treatment included wound debridement and daily dressings with sulphadiazine. The skin took 14 days to heal (Lagey et al 1995).

Even close contact with animals that have been among H. mantegazzianum can result in problems, as when a woman developed phytophotodermatitis from contact with a cat that had been playing with H. mantegazzianum (Camm et al 1976). There was no mention of the cat experiencing any discomfort however.

Children, strimmer operators, gardeners, walkers, mountain bikers and fishermen probably comprise the main risk groups for phytophototoxidty. They are unlikely to seek medical advice until the skin effects are severe, several hours or a day or two after exposure. Management is symptomatic and supportive. Wet compresses and paraffin gauze dressings may help to reduce swelling and inflammation. Systemic or topical corticosteroid preparations can help to relieve irritation (Anon 1970). In severe cases, hospital admission may be required for analgesia and supportive care.

Hyperpigmentation requires no treatment but affected areas can remain sensitive to sunlight for several months or years, so continued use of sunscreen is advised (Lovell 1993). If seen shortly after exposure, the skin should be washed thoroughly with soap and water to remove plant sap (Gunby 1980) and protected from sunlight by covering or applying sunblock, or both, until at least 48 hours post-exposure even if asymptomatic.

Psoralens are not destroyed by cooking (Ivie et al 1981), and can be absorbed from the gut. Two psoralens, 8-methoxypsoralen and 5- methoxypsoralen, are used medicinally both orally and topically as photosensitisers before ultraviolet A therapy for treating psoriasis, vitiligo and T-cell lymphomas.

Table 1 .Examples of psoralen-containing plants that can cause phytophototoxicity

Ingestion of large amounts of psoralen-containing plants can sensitise the skin to sunlight and result in phytophototoxicity, and such a case has been described from eating celery (Apium graveolens) (Ljunggren 1990). A 65-year-old woman spent 30 minutes on a sunbed one hour after eating a large guantity of cooked celery. The next morning her skin was slightly red and burning. Within 48 hours of exposure, she was admitted to hospital with pyrexia, generalised intense erythema, multiple large blisters and oedema. Unexposed skin was unaffected. Topical and systemic corticosteroids were given and the reaction subsided over two weeks. During the healing phase the skin was very painful, corresponding to one of the side effects of photochemotherapy.

Ingestion of St John's Wort (Hypericum species) is a well known hazard to grazing animals, causing severe phototoxicity (Lovell 1993), a direct toxic effect of a compound known as hypericin. The use of St John's Wort (H. perforatum) extract in humans as an antidepressant at high or very high doses may result in photosensitisation as a rare adverse drug reaction (Brockmoller et al 1997, Greeson et al 2001).

IRRITANT SAP

Some plants pose a risk when they are pruned because their sap is irritant. Many Euphorbia species are known for their irritant sap, and skin and eyes should be protected if cutting these. Skin reactions are not always immediate and vary in severity. Initially there is erythema and pruritus, then oedema and possibly blistering. Blisters vary from small pustules to large bullae and usually crust over withinin one to three days unless there is secondary infection. Recovery is usually complete withinin four to seven days without scarring (Spoerke and Smolinske 1990).

If sap enters the eyes, severe irritation may occur. Clinical features include pain, lacrimation, lid swelling, keratitis, iritis, decreased visual acuity, severe conjunctivitis and temporary blindness (Grant and Schuman 1993). Treatment should include irrigation with saline or water, a fluorescein stain to assess damage and referral to an ophthalmologist if necessary. Antibiotics and steroids may be required in severe cases.

ALLERGIC REACTIONS

Local skin effects and systemic reactions may be experienced with allergic responses to plants. Allergic reactions have be\en reported for a large range of plant species, and an occupational hazard for florists and horticulturalists dealing with particular plants in bulk is the development of sensitisation to a particular species. Classic examples of plants causing occupational problems include tulips and the pot plant, Primula obconica.

Tulip bulbs can cause allergic contact dermatitis known as 'tulip finger' (Bertwistle 1935). They contain several chemical compounds including tuliposide A, which appears to be the main sensitiser (Bruynzeel 1997). Tulip finger' is characterised by painful tingling and erythema of the fingertips, particularly around the fingernails, developing within 24 hours of handling bulbs. Granulation tissue develops under the nails, which become brittle and may be lost. In sensitised individuals, there may be hyperkeratotic fissuring eczema under the nail plate that may spread to the fingertips. Secondary spread to the arms, face and genitalia occasionally occurs. Treatment is symptomatic and supportive. Wearing gloves when handling bulbs may help, and keeping fingernails short and using emollients can also improve the condition. Avoiding the plant completely may be necessary in severe cases.

Skin reactions to P. obconica have been documented for more than a century (Oldacres 1889). The plant is covered in tiny allergen- containing hairs. Allergic contact dermatitis is common, usually affecting the fingers and face (Logan and White 1988) with redness and swelling of the eyelids and around the mouth, neck, arms and hands. More rarely, patches may appear on the ears, thighs, buttocks and ankles. The rash may cause burning or itching and there may be oedema and blistering. Distinctive patterns of blotches and linear streaks are often seen, particularly on the arms and forearms (Rook and Wilson 1965). These allergic reactions should be managed conventionally.

Table 2. Summary of reactions to plant exposure

A widespread plant causing allergic and irritant dermatitis is ivy (Hedera species). Contact can result in a bullous eruption that may be linear or streaking. Gardeners and florists are most likely to experience this, but it can also be seen in children. A four- year-old boy developed itchy dermatitis with burning on the left side of his face and chin, neck and pre-sternal area with vesicular and erosive lesions on an erythematous base. Two days earlier he had been climbing a wall covered with ivy (H. helix) (Massmanian et al 1988).

Allergic reactions are described for various vegetables, including potatoes, asparagus and celery. Potatoes (Solanum tuberosum) can cause contact urticaria and dermatitis (Hannuksela and Lahti 1977) but the allergen is unknown. Asparagus (Asparagus species) can also cause contact dermatitis (Lovell 1993) and allergic contact urticaria with erythema and pruritus. Asparagus sensitivity may also result in itchy eyes, conjunctivitis and eyelid oedema.

Celery consumption before vigorous exercise has been known to cause both dermal and systemic effects. In one case, a 20-year-old man described a six-month history of generalised pruritus, nasal obstruction, dyspnoea, swelling of the lips, massive urticaria, hypotension and extreme weakness occurring within five to ten minutes of beginning strenuous exercise if he had ingested celery in the previous two hours. He displayed a positive skin prick test to celery. Further anaphylactic episodes were avoided by excluding celery from his diet when exercising (Kidd et al 1983). It would seem that celery is a vegetable to treat with caution if exercise or sunbathing are on your agenda.

Another example of a rare allergic reaction is allergic contact dermatitis from grasses (Koh et al 1997). More common is 'grass intolerance', which presents as itchy, patchy or streaky, red, non- bullous dermatoses that can persist for several days after prolonged contact with grass. Even more exceptional is a report of anaphylaxis on skin exposure to grass.

A 33-year-old man suffered rapidly progressing pruritus, generalised urticaria, rhinoconjunctival mucous membrane swelling, hypotension, tachycardia, collapse and wheezing within five minutes of a dramatic grass slide, involving considerable skin-grass contact, during a football game. There was a previous history of grass pollen allergy and contact urticaria (Miesen et al 2001). Haymaking, rugby or tennis at Wimbledon are not recommended in these cases.

MECHANICAL DAMAGE

A very basic skin problem associated with plants is simple mechanical damage. Anything with thorns can inflict pain, scratches and lacerations with a possibility of secondary infection.

Blackthorn (Prunus spinosa) is notorious for causing penetrating wounds and sepsis (Lovell 1993). The thorns are very long, hard and sharp, creating a hazard for those gathering sloes, the fruit for making sloe gin. Blackthorn thorns have a reputation in country lore of being 'dirty' thorns, possibly due to the habits of some bird species that impale insects and larger food items on them. Such thorns may be a convenient and protected larder for birds but can be particularly liable to cause unpleasant infections in humans.

Indoors, cacti are the plants most likely to cause mechanical damage. A variation on the basic sharp, pointy spine theme is seen in bunny ears (Opuntia microdasys). This cactus is covered with glochids (bristles), which can penetrate the skin when the plant is touched, resulting in irritation, dermatitis and occasionally granuloma formation. The plants are covered in a regular pattern of small tufts each of which may contain over 100 glochids, which are between 3mm and 6mm long, have sharp, spear-shaped tips and are covered in microscopic barbs. Touching the plant leads to glochids penetrating the skin and pulling them out results in the barbs tearing away and remaining in place. The resultant discomfort, itching and burning can persist for up to a week. Small papules, in which the glochids may be visible as central pinpoint-sized black dots, can develop and usually clear within two weeks (Whiting and Bristow 1975).

The papules occasionally progress to granulomas, developing gradually up to four weeks post-exposure, and may be an allergic response to antigens in the glochids (Schreiber et al 1971) or a non- specific foreign body reaction (Snyder and Schwartz 1983). The granulomas can persist for two to eight months before resolving spontaneously (Schreiber et al 1971).

Experiments using shaved rabbits have suggested that a combination of tweezers and water based glue is the best way of removing glochids (Martinez et al 1987). Large clumps can be removed with tweezers, and a thick layer of water based household glue is spread over the rest, covered with gauze, allowed to dry and then peeled off (Gelbard 1984). This combination has been shown to remove 99 per cent of glochids (Martinez et al 1987).

Other methods include using peel-off facial masks (Putnam 1981) and depilatory wax, melted in a microwave, applied warm and peeled off after two minutes (Schunk and Corneli 1987). Sedation may be required to facilitate glochid removal in distressed children. Removal with adhesive tape is not recommended because, although it can remove some glochids, it pushes others deeper into the skin resulting in more inflammation than if removal was not attempted at all.

CONCLUSIONS

Although generally harmless, plants are not necessarily good for the skin. Table 2 summarises points covered here and, while many of these reactions are extremely rare, they are worth remembering.

Apparent whiplash or cigarette burn marks are not necessarily signs of non-accidental injury, as in the case of an eight-year-old girl described in the literature. She had been playing in a patch of wild parsnips on a sunny day wearing only knickers. The family was under surveillance by social services owing to previous child neglect and the girl was visited ten days later by her social worker, who was alarmed to see linear lesions resembling whip marks, mainly on the trunk but also on the forehead, hands, arms, thighs and lower legs.

She was seen in hospital the same day, and the extensive, dusky red and blistering skin lesions and areas of brown hyperpigmentation were recognised as phytophotodermatitis (Campbell et al 1982).

Most plants mentioned here cause problems only rarely, and even nettles, despite their unpleasant stinging propensity, are not without their uses. Young shoots can be cooked and eaten as a vegetable or soup, as boiling inactivates the irritant chemicals. The older shoots are stringy, so not particularly palatable but apparently have a useful laxative effect (Dobson 1979). As if that were not enough, nettles can be made into wine and beer, and the fibrous parts can be woven into cloth. But remember to wear gloves when picking the raw materials!

References

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Bertwistle A (1935) Tulip fingers'. British Medical Journal. 2, 255.

Bombardelli E, Morazzoni P (1997) Urtica dioica L Fitoterapia. 68, 387-402.

Brockmoller J et al (1997) Hypericin pseudohypericin: pharmacokinetics and effects on photosensitivity in humans. Pharmacopsychiatry. 30, 2, 94-101.

Bruynzeel D (1997) Bulb dermatitis. Dermatological problems in the flower bulb industries. Contact Dermatitis. 37, 2, 70-77.

Camm E et al (1976) Phytophotodermatitis from Heracleum mantegazzianum. Contact Dermatitis. 2, 68-72.

Campbell et al (1982) 'Non-accidental injury' and wild parsnips. British Medical Journal. 284, 708.

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Freeman K et al (1984) Strimmer rash. Contact Dermatitis. 10, 117- 118.

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Gunby P (1980) Keep away from that 'tree,' folks! Journal American Medical Association. 244, 2596.

Hannuksela M, Lahti A (1977) Immediate reactions to fruits and vegetables. Contact Dermatitis. 3, 79-84.

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Kidd J et al (1983) Food-dependent exercise-induced anaphylaxis. Journal of Allergy and Clinical Immunology. 71, 407-411.

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Kulze A, Greaves M (1988). Contact urticaria caused by stinging nettles. British Journal of Dermatology. 119, 269-270.

Lagey K et al (1995) Burns induced by plants. Burns. 21, 542- 543.

Lovell C (1993) Plants and the Skin. London, Blackwell Scientific Publications.

Lown J, Sim S (1978) Photoreaction of psoralen and other furocoumarins with nucleic acids. Bioorganic Chemistry. 7, 85-95.

Ljunggren B (1990) Severe phototoxic burn following celery ingestion. Archives of Dermatology. 126, 1334-1336.

Logan R, White I (1988) Primula dermatitis: prevalence, detection and outcome. Contact Dermatitis. 19, 68-69.

Martinez T et al (1987) Removal of cactus spines from the skin. A comparative evaluation of several methods. American Journal of Diseases of Children. 141, 12, 1291-1292.

Massmanian A et al (1988) Contact dermatitis from variegated ivy. Contact Dermatitis. 18, 4, 247-248.

Miesen W et al (2001) Anaphylaxis on skin exposure to grass. Allergy. 56, 799.

Oldacres C (1889) Toxic symptoms produced by handling Primula obconica. British Medical Journal. 2, 719.

Oliver F et al (1991) Contact urticaria due to the common stinging nettle (Urtica dioica) histological, ultrastructural and pharmacological studies. Clinical and Experimental Dermatology. 16, 1-7.

Putnam M (1981) Simple cactus spine removal. Letter. Journal of Pediatrics. 98, 333.

Reynolds N et al (1990) Strimmer dermatitis. British Journal of Dermatology. 123, 37, 63.

Reynolds N et al (1991) Weed wacker dermatitis. Archives of Dermatology. 127, 1419-1420.

Rook A, Wilson H (1965) Primula dermatitis. British Medical Journal. 1, 220-222.

Schreiber M et al (1971) Cactus granulomas of the skin. An allergic phenomenon. Archives of Dermatology. 104, 4, 374-379.

Schunk J, Corneli H (1987) Cactus spine removal. Letter. Journal of Pediatrics. 110, 4, 667.

Snyder R, Schwartz R (1983) Cactus bristle implantation - report of an unusual case initially seen with rows of yellow hairs. Archives of Dermatology. 119, 152-154.

Sommer R, Jillson O (1967) Phytophotodermatitis (solar dermatitis from plants). Gas plant and the wild parsnip. New England Journal of Medicine. 276, 1484-1486.

Song P, Tapley J Jr (1979) Photochemistry and photobiology of psoralens. Photochemistry and Photobiology. 29, 1177-1197.

Spoerke D, Smolinske S (1990) Toxicity of Houseplants. Boca Raton FL, CRC Press.

Frances Northall RGN, BSc, is an information officer at the National Poisons Information Service, London

Copyright RCN Publishing Company Ltd. Jun 2003

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