Vol. 3 No. 1 September 20, 1982

I. Plants, Pesticides and Other Toxic Chemicals: Cutaneous Toxicity (Toxic Effects on Skin)

I would like to express thanks to Dr. Molly Coye, Medical Officer for NIOSH for allowing the use of information on cutaneous toxicity that she developed for inclusion in a course syllabus entitled "Pesticide Training: Continuing Education Seminar for Health Personnel", published by the Interagency Pesticide Training Coalition.

Cutaneous toxic reactions account for approximately 1/3 of all pesticide related occupational problems. Poison oak dermatitis is the most frequent cause of temporary disability in forestry workers. Dermatitis means literally inflammation of the skin. Inflammation is a tissue response to cellular injury which consists of varying degrees of pain, redness, heat, and swelling. Most often dermatitis is referred to as a skin "rash", however, this term is very non-specific. There are many different types of "rashes" and they differ quite a bit in the way they appear and in how they are produced. In this newsletter we will discuss some of the most frequently encountered dermatitis problems in humans and food animals.

1. Primary Irritant Dermatitis. (PID)

This type of dermatitis is caused by chemical substances that directly irritate the skin (like caustic acids or bases). The manifestations may be similar to a slight burn (redness, itching, pain) or as severe as blisters, peeling and ulcerations of the skin. The areas of direct contact are usually the most affected and this is one of the ways it is recognized. Treatment entails removal of the irritant by washing and preventing further contact with the chemical. Steroid creams (such as 0.5% hydrocortisone preparations, available without prescription) will help alleviate pain and itching.

The following plants and pesticides may cause primary irritant dermatitis.


Sulfur Captafol Endosulfan
Omite Folpet Lindane
Ziram Organophosphates Toxaphene
Thiram Methomyl Kelthane
Zineb Dinoseb Triazine
Maneb Dinitro Benomyl
Captan TOK Glyphosate
Weed oil Chloropicrin Dacthal


Plants Flowers Trees
Tomato Dieffenbachia Rubber Tree
Carrot Castor bean Fig Tree sap
Mushroom (Fungi) Daffodil Milkweed sap
Cucumber Buttercup  
Parsnip Foxglove  
Turnip Tulip bulb  
Parsley Narcissus bulb  

2. Allergic Contact Dermatitis ( ACD )

The best example of ACD is poison oak and poison ivy dermatitis. The skin is sensitized by exposure to the chemical (once or many times) and the result is a localized allergic reaction. Workers may handle an allergenic substance for years before ACD develops, or it may develop after a single exposure. The symptoms vary from redness, itching and small blisters (vesiculation) to widespread blisters that overlap forming very large fluid filled blisters (bullae). Treatment entails thorough washing to remove the allergen followed by treatment to reduce the itching pain and swelling. Topical corticosteroid creams may be very effective in reducing the symptoms. When large blisters break or are opened, care should be taken to prevent secondary infection of these denuded (raw) areas. Local anesthetic creams (containing benzocaine) should be avoided since they also can act as contact sensitizers and also may delay healing.

The following plants and pesticides have been reported to cause ACD.


Captan Captafol
Benomyl Triazine
Dichlorvos Parathion
Malathion Naled
Some natural pyrethroids Thiram
Zineb Maneb


Plants Flowers Trees
Rhus- Primrose Cedar
Poison Ivy English Ivy Pine
Poison Oak Chrysanthemum Lichens
Poison Sumak Tulip bulbs  
Liverwort Narcissus bulbs  

3. Photosensitization Dermatitis (There are two basic types)

a) Photo-toxic Photosensitization Dermatitis-Phototoxicity is not very common in humans whereas in domestic food animals it is the most common cutaneous toxic response. Phototoxic photosensitivity occurs when a photosensitizer is present in the body and only after exposure to sunlight. The signs are sunburn like reactions especially in non-pigmented areas. Swelling and blistering (big head in sheep) may be severe enough to cause large denuded areas which are susceptible to secondary infection. In ruminants two types are seen, direct and indirect. Direct photosensitization occurs when the chemical substance is directly responsible for causing the reaction following activation by sunlight. Examples of direct photosensitizers are phenothiazines, TTC's, Klamath weed (Hypericum perforatum), which contains hypericin; Smart weed; (Polygonum); Buckwheat (Fogopyrum); Spring parsley (Cymopterus watsoni); and Bishops weed (Ammi majus).

Indirect phototoxic photosensitization in ruminants is always associated with liver damage. In ruminants one of the breakdown products of chlorophyll is phylloerythrin, a photodynamic agent activated by sunlight. Usually the healthy liver detoxifies and excretes absorbed phylloerythrin before it reaches the general circulation because all the blood from the intestines passes through the liver before it goes to the heart. If the liver is damaged sufficiently, enough phylloerythrin may reach the general circulation to cause photosensitization upon exposure to sunlight. The ultraviolet rays in sunlight activate the phylloerythrin to a product that causes damage to the skin.

Some of the conditions and plants which cause indirect phototoxic photosensitization are:

Treatment: Reduce chlorophyll intake by removing from lush pasture. Keep in shade.

Contact phototoxic photosensitization is the most common occupational phototoxic reaction in humans. Plants which cause it are:

The symptoms are redness, pain, blistering and following recovery, hyperpigmentation of the affected area. Historians record that the ancient Egyptians knew of this reaction and used it to darken light areas of the skin. Derivatives of the toxic furocoumarins from these plants are still used today to treat hypopigmentation(abnormally light pigmentation of the skin).

b) Photoallergic:

This disorder is very similar in appearance to allergic contact dermatitis, however, sunlight is required to initiate the process. It requires prior exposure to the chemical and sunlight, and it is not very common. Phenothiazines may cause photoallergic toxicity. Treatment is the same as that used for ACD.


Cutaneous reactions to toxic compounds have manifold causes. Determination of just what has caused the dermatitis may involve "patch testing" in which the patients skin is exposed to small patches containing dilute solutions of the suspect agents. In this way, the offending chemical can be identified and measures taken to prevent or minimize future exposure.


A relatively unknown but apparently very potent plant which produces dermatitis is the Century plant (Agave parryi). Last May, Frank Brucato of Contra Costa County called about a few persons who suffered from dermatitis after cutting up a Century plant with a chain saw. He forwarded me a report by a Mr. McDonald of Pittsburg, Mr. McDonald had extensive contact with juice from the plant and the areas started to burn within a minute. He immediately washed with soap and water with no relief. Within 24 hrs. small red bumps appeared that were very painful. He stated that the bumps came to a head 2 days after first contact and that the bumps were still there 5 days later. After 12 days the dermatitis had resolved leaving only small, light red spots. I spoke to Mr. McDonald in August and he stated that the spots did not disappear until 4 weeks after exposure. In the true scientific tradition, Mr. McDonald and a few others tested the juice of the plant on their arms and obtained the same result.

Thus the juice of the Century plant appears to be an extremely potent irritant to human skin. Caution should be exercised to prevent contact with the juice when trimming or cutting up the plant. I have not been able to find any reports that have detailed the mechanism by which Century plant produces this severe dermatitis.

( I encountered the following reports of skin problems while I was writing this newsletter and they seemed appropriate for inclusion.)

Cercarial Dermatitis among Bathers in California

Cercarial dermatitis - California: In late August 1981, four persons sought medical attention for dermatitis after swimming or wading in a cove of the Mad River at Camp Bauer in Humboldt County, California, 10 miles from the Pacific coast. Subsequent investigation uncovered 12 additional cases later diagnosed as cercarial dermatitis. The most common complaint was pruritis (itching) occurring within 1 1/2 hours after water contact. Discomfort ranged from moderate to severe. In a few persons, pruritis persisted several days; those patients were treated with antipruritics(drugs which alleviate itching). Those with proven S. mansoni were treated with a single dose of oxamniquine(30 mg/kg).

Editorial Note: Schistosome life cycles are characterized by asexual reproduction in an extremely restricted range of snails (intermediate host) and sexual reproduction (oviposition) in a restricted range of vertebrates (definitive host). Vertebrates become infected when free-swimming furcocercous (fork-tailed) cercariae emerge from snails and penetrate the skin, losing their tails and becoming schistosomulae (juvenile worms). Man was not a suitable, definitive host in the first outbreak, and the schistosomulae died in the skin, initiating cercarial dermatitis (schistosome dermatitis, swimmer's itch, clam digger's itch, sea bather's itch). Many species of schistosomes throughout the world may produce this syndrome, including some parasites of sea birds and marine snails. Usually, onset of pruritic, papular rash occurs within a few hours after bathing and may be preceded by a stinging sensation just after exposure. Symptoms are probably due to the host's reaction to the dead and dying schistosomulae and may persist for several days but always resolve spontaneously. Treatment with antihistamines or antipruritics may provide relief. In the cercarial dermatitis outbreak, the demonstration of infected snails at the suspected site of exposure was convincing evidence for that diagnosis, as well as for incrimination of the river as the first source of that type of infection documented in California.

(Morbidity and Mortality Weekly Report, August 20, l982 / Vol. 31 / No. 32.)

Don't Get Too Clean, It May Be Dangerous To Your Health

Small children, as well as certain cults, will be pleased to hear that perhaps too much "cleanliness" can be dangerous. The causative factor is not actually "cleanliness" but the bacterium, Pseudomonas, which can lead to a form of dermatitis, now being experienced by persons who soak in hot baths. Their skin becomes superhydrated and permits the bacteria to enter the hair follicles. Symptoms of the ailment are reddening of the skin, spotty rashes, itching, (described as that produced by several dozen mosquito bites), eye and ear irritation and, at times, nausea.

It is estimated that over 100,000 tubs of various makes and materials are being used and many new and even older homes are installing these "spas".

Before persons tear out their spa or whirlpool bath, they should consider paying more attention to thorough cleaning of the bath, in particular those baths constructed of red wood. These red wood baths should be chlorinated, treated with acid, and filters should be changed frequently to eliminate the pseudomonas.

Newsletter, Forum For the Advancement of Toxicology, Vol. 15/No. 2, May 1982.