• Define Rhus dermatitis.
• Understand the cause of poison oak dermatitis.
• Identify means of reducing the risk of acquiring Rhus dermatitis when avoidance of the plant is not possible.
• Identify barrier and decontamination options.
• Identify treatment options.
• Identify safe means of dealing with dust, pollen and grass allergies.
• Define the Hymenoptera class of stinging insects.
• Distinguish localized from systemic venom reaction.
• Distinguish systemic venom reaction from allergy and anaphylaxis.
• Assess the risk of tick-borne diseases during wildland firefighting.
• Review ways to identify and treat Lyme disease.

In part I of this two part series we tried to address some of the most common hazards encountered during wildland firefighting deployments and strategies to deal with them. One very common problem that needs to be covered is contact dermatitis from poison oak. There are also a few unusual problems worth discussing. Bites and stings from animals, snakes and insects, as well as tick borne diseases (like Lyme disease) are either very unusual or may present limited risk to the firefighter. However allergy to insect stings is a potentially serious problem. We’ll discuss other causes of allergic reactions as well as some advice for dealing with bee swarms. With the exception of dermatitis, many of these things are less likely to be a problem during wildland firefighting, however it is sometimes the uncommon problems that can bring an operation to a halt. So we’ll take a look at some of them.

In this newsletter:

Contact Dermatitis (poison oak) and Other Allergies

Bites and Stings

(bees, fire ants, anaphylaxis; ticks, Lyme Disease)

Anything that causes an allergy-related rash after contact with the skin is called contact dermatitis. We’ll focus on the most common cause in wildland firefighting, which is poison oak (a member of the Rhus genus of plants). Members of this group of plants include poison ivy, poison sumac and poison oak. Poison oak dominates west of the Rocky Mountains and below 4000 feet. A large percentage of the population is sensitive to poison oak, up to 50% according to some authors. And about 15-25% have serious reactions, enough to temporarily prevent them from working. The component of the plant that is responsible for the skin reaction is a light oily resin called urushiol present throughout the entire plant. This resin penetrates the skin and sets up a reaction in the skin that later forms the characteristic vesicular or bullous rash (small fluid filled blisters).

The rash does not occur immediately after contact, however. Rhus dermatitis is a cell-mediated allergy which causes T-lymphocytes to react over a period of 2-10 days. The rash appears most often 3 or 4 days after exposure. Since it is not mediated by histamine, antihistamines are not particularly helpful in treatment. It is characterized by red, raised, itchy patches or linear or clustered vesicles (small fluid-filled blisters). The fluid within the vesicle is an inflammatory fluid created by the body from the allergic reaction. It will not further spread the rash if the vesicle is ruptured and the fluid leaks out. What can happen though is that gloves, clothing, shoes or tools contaminated with the resin can initiate a new skin reaction in proximity to an existing rash or at a new site. Scratching and opening the rash can set up a secondary skin infection unrelated to the allergic reaction.

The resin boils at about 200C (about 390F) so under fire conditions it may splatter onto soot particles which when airborne could be inhaled and result in respiratory swelling. This has rarely been reported but is theoretically possible. Contaminated soot particles could cause conjunctivitis or tracheobronchitis. In the absence of asthma or other underlying lung disease, inhalation injury or facial burns, this is one possible cause of respiratory compromise developing in an otherwise healthy firefighter several days into firefighting operations when there is still open burning of fuel with soot production.

More likely, skin exposure to poison oak occurs during the cutting of fire line and the contamination of nomex, gloves, tools and equipment with the resin. That resin can then be transferred to the skin through contact with the contaminated material and lead to the characteristic rash. The face, neck, forearms and hands are the most likely areas to be affected, but the resin can be spread to any part of the body from contamination on the hands. Hand washing and avoiding subsequent contact with potentially contaminated gloves, boots, tools & nomex until the next operational period will help to reduce exposure. Protective gear itself provides barrier protection to the resin, but the resin can persist on this equipment and lead to secondary exposure. It’s interesting to note that the resin is soluble in rubber gloves & will penetrate through to the skin. Once there the occlusive nature of the rubber glove and the sweat beneath the glove propagates the spread of the resin more widely over the hand. Vinyl gloves appear to be protective against resin penetration. Awareness of equipment contamination and hand washing are the most fundamental means to minimize the risk of contact with the resin when avoidance of the plant is impractical or impossible.

The resin is soluble in organic solvents like acetone or isopropyl alcohol (rubbing alcohol) used to prepare IV sites, but if a solvent is used be sure to use enough to flush the hands or tools well. Too small a volume of solvent may just spread the resin around rather than remove it. Tec Laboratories markets Technu which is a mineral spirit/polyalcohol combination used to decontaminate skin and tools after exposure. Clothing and protective gear act as a barrier to the resin. Barrier preparations for application to the skin are also available. Barrier preparations make delayed washing with soap and water or even water alone more effective in resin removal. One commercial product is a linoleic acid dimer called Stokogard Outdoor Cream. Another barrier product from Tec Laboratories is Armor. Barrier products should be applied to exposed or potentially exposed skin areas before exposure and periodically while on the fire line until water washing is possible. They can also be applied to clothing and protective gear likely to come in contact with the poison oak plant and then the skin at some later time, like shirt and pants cuffs. So protection from exposure to poison oak is a combination of protective gear, barrier preparation application before exposure (like Armor) followed by solvent (Technu, isopropanol) and water wash after returning to fire camp or whenever practical.

Once the rash develops it pretty much has to run its course. Over-the-counter products like CalaGel or Calamine Lotion can help in mild cases to dry the rash and provide some relief from the itching. Oily occlusive creams should not be used because they will hold in the moisture and not allow the rash to dry. Topical antihistamines don’t really contribute to symptom relief, although they are marketed in products like CalaGel and some forms of Calamine Lotion. It is probably better to use the form of Calamine Lotion without the antihistamine additive. The major benefit of these lotions is their drying properties on the rash. Nonprescription antihistamines may help with itching somewhat but all are sedating, so balancing symptom relief with fireground safety is important. Prescription less-sedating antihistamines are a safer option for itching. Topical steroid creams are also of limited effectiveness except for the most minor rash. In more severe or extensive cases steroids like prednisone, to suppress the immune response, will be necessary. High oral doses of steroids seem to be as effective as steroid injections according to some authors. The important thing here is that if you are ever prescribed steroids for a mean case of poison oak be sure to finish the full prescribed course of up to 15 days. The rash will usually begin to improve as soon as 18 hours and be noticeably better 2-3 days after starting steroids, but if they are discontinued early it can return as bad or worse than before.

You can imagine that any number of possible allergies could contribute to discomfort in fire camp or on the fire line. Dusts, pollens and grasses are the most likely. More important than the cause, since little can be done to reduce exposure, is the choice of treatment. As mentioned earlier, all over-the-counter antihistamines are sedating. They can compromise fire line safety, especially when combined with fatigue or darkness. Probably the safer first choice for runny nose and congestion due to allergies is an over-the-counter decongestant. Some underlying problems like hypertension can be aggravated by decongestants so check the precautions on the bottle. Nighttime use of antihistamines in fire camp is safer than use on the fire line and may be an alternative for symptom relief between operational periods. Prescription less-sedating antihistamines may be a reasonable choice if symptoms are distracting enough. Even these are slightly sedating so a personal evaluation of risk versus benefit is necessary. One of the more potentially serious allergies in susceptible persons is bee sting allergy. We’ll address that next.

There has been a lot of press lately about the evolving problem of Africanized honeybees in southern California. It’s probably realistic that a hive of Africanized honeybees could be encountered in the wild or in an outbuilding at an urban-wildland interface. Hives are showing up in distinctly urban areas as well. Their uniqueness is their aggressive swarm in response to a direct disturbance or somewhat more remote stimulus like vibrations from an internal combustion engine (lawn mower). They also seem to exert aggressive defensive behavior in response to carbon dioxide. This may be one reason for the increased risk of facial stings from a swarm. Beyond their defensive behavior, however, Africanized honeybees (AHB's) venom is no more likely to stimulate an allergic reaction (antigenic) than European honeybees. AHB's have the same amount or volume of venom as European honeybees do. Urban defense of a victim encountering a swarm of Africanized honey bees has been based on the use of a fog pattern surfactant, like class A foam or AFFF, which lowers the surface tension of water and coats the bees. This low surface tension water coating initially inhibits their ability to fly and covers the respiratory surfaces of the bees, which kills them. Theoretically a soap and water solution will work as well but spraying a soap into the environment, except possibly for a lifesaving maneuver, violates environmental protection laws. Only the insecticidal soap called M-Pede is approved by the California Environmental Protection Agency for emergency mitigation. Water fog alone may temporarily disengage the swarm but it will not incapacitate the bees and the hazard will still be present.

There are two syndromes possible from bee stings, allergy and venom reaction. Since European honeybees tend not to swarm or sting in the numbers that Africanized honeybees do, the venom reaction is typically limited to local redness, itching and pain at the sting site. This is usually a self-limited reaction requiring no specific therapy. If the stinger is still attached it is recommended that it be scraped off with a knife blade or other rigid tool (even the edge of a credit card) as the stinger can continue to inject venom for up to 10 minutes after the sting occurs. Squeezing the stinger (i.e. with fingernails or tweezers) to pull it out may actually inject more venom from the attached venom sac left behind with the stinger. When either the European or Africanized honeybee stings, the barbed stinger is left in the victim, essentially eviscerating and eventually killing the bee. Multiple stings from a swarm of either bee, though more likely the Africanized honeybee, can lead to systemic symptoms from venom overload alone. Children and the elderly or those with significant underlying health problems are the most susceptible. Applying ice to a local isolated sting site will help reduce discomfort. Antihistamines for itch and Tylenol or Motrin for pain may also help. The greater anti-inflammatory effects of Motrin give it a theoretical advantage over Tylenol. Massive bee envenomations (venom overload) can lead to systemic reactions like kidney failure, shock, intravascular hemolysis and liver injury which can be fatal even if the person has no allergy to the proteins in the venom. The onset of systemic symptoms can be delayed up to 24 hours after envenomation. It is estimated that 50 stings may lead to symptomatic envenomation. 19 stings per kilogram of body weight has been suggested by some authors as the median lethal "dose" of venom. This equates to a 50% fatality rate with approximately 500-1400 stings in a 75kg adult.

Allergy and anaphylaxis is a different story. In a susceptible person a single sting can lead to significant symptoms. Unlike systemic envenomation, anaphylaxis will have a more rapid onset usually with symptom onset within half an hour after the sting. It has been estimated that 0.4-0.8% of the population is allergic to insect stings. Biting insects rarely cause allergy or anaphylaxis since no protein-containing venom is injected. Cross reactivity does occur between the venom of insects within Hymenoptera. Unfortunately, the early symptoms of systemic envenomation and anaphylaxis can be similar. If anaphylaxis is the problem, those symptoms can rapidly progress to life-threatening airway and hemodynamic problems. The symptoms of systemic envenomation progress more slowly. Anyone acutely symptomatic from one or only a few stings should be treated for allergy or anaphylaxis, depending on the severity of the reaction. Someone stung multiple or even hundreds of times now presenting with acute symptoms should probably also be treated initially for allergy or anaphylaxis because waiting to see how the symptoms progress can result in the rapid evolution of airway and respiratory compromise that may have been preventable with earlier treatment.

Anyone with a known sensitivity to hymenoptera sting should carry one of the commercially available versions of epinephrine, unless there is some other medical contraindication to its use. Among those available now are EpiPen (an epinephrine autoinjector) and the AnaKit (an epinephrine autoinjector and an antihistamine). At the time of this writing the AnaKit has been temporarily recalled for a manufacturing problem. This brings up a practical problem. The use of epinephrine autoinjectors is not part of the scope of practice for EMT-B’s in California. So if you know you are allergic to hymenoptera sting, or believe you might be, then it is wise to carry your own epinephrine autoinjector prescribed by your doctor. If a paramedic is among the strike team members, as there should be for in-county strike teams, then this is not a problem. This could come up though in out-of-county strike teams. Just to complete the picture, if a paramedic needs to provide ALS care in a remote location for any emergency and doesn’t have base hospital communications or can’t reach a repeater, that medic can use the entire Orange County scope of practice under the communications failure SOP. Just fill out the Report of ALS Services Provided Without Base Hospital Contact (O.C. EMS Policy 330.15) when you get back to fire camp. According to OCEMSA policy this report should be made available to your usual base hospital within 24 hours of the treatment given, but this may be difficult during remote wildland operations. The Medical Unit or the Logistics Section may be able to help if you have phone numbers. When working out-of-county, this same practice applies. We can operate under Orange County treatment guidelines regardless of the location of the fire incident. As usual, try to get a PCR done sometime to send with the patient or forward to the receiving hospital. This may also be tougher during wildland operations, but logistics should be able to help you get the documentation to the right places eventually.

Another addition to the Hymenoptera hazard in Southern California is the imported fire ant. Because of venom cross reactivity, a person with bee venom allergy may also react to the venom of the imported fire ant. This is the biggest risk. The imported fire ant is unique in that it bites and holds on to the skin with its mouthparts and then stings in a characteristic semicircular pattern with an abdominal stinger. In the absence of allergy, the symptoms are usually limited to localized redness, pain and sterile pustules in a semicircular pattern.

Keep in mind that stinging insects may be as much a hazard in fire camp as on the fire line. Food, beverages and trash can attract insects and present a sting hazard when our protective instincts are lowered somewhat between operational periods. Using insect repellant, like DEET, may help reduce the risk of insect stings and bites however they will not inhibit a swarm.

A vaccine against Lyme disease has been recently introduced and heavily marketed and has raised the question of its use in firefighters who may be involved in wildland firefighting operations. Lyme disease is one of several bacterial diseases transmitted from the bite of ticks. It is not a common disease in California. More than 80% of cases nationwide originate in 8 states (New York, New Jersey, Connecticut, Rhode Island, Maryland, Massachusetts, Pennsylvania and Wisconsin). In fact the California Department of Health Services (DHS) lists only the northern coastal area as "modest risk". The Bay Area and the Central Valley are considered "some risk" while all of Southern California is considered "no or low risk". Presently DHS does not recommend routine vaccination against Lyme Disease anywhere in California. By current DHS guidelines the vaccine should be considered only for frequent or prolonged contact with natural vegetation in the modest risk area of the Northern California coast. Preventive measures against tick bites and antibiotic treatment early in the disease are the approaches to Lyme Disease prevention and treatment in the relatively lower risk state of California.

Lyme Disease is a bacterial disease resulting from the bite of an infected Western Black-legged tick. It takes at least 12-24 hours, sometimes up to 72 hours, of tick feeding to transmit the disease to humans. If the tick is discovered and removed before this the risk of disease is reduced. The disease is characterized initially in about 80% of cases by a red, slowly migrating (over days to weeks) rash (erythema migrans), sometimes with central clearing, originating at the tick bite site. The greatest number of cases occur during tick season, May through September with a peak incidence in June and July. Fortunately this is earlier than our usual wildland fire season. At this stage the disease is treatable with oral antibiotics like amoxicillin or doxycycline. If the disease is suspected but the rash is not typical, serologic testing can determine the presence of infection. If untreated, the disease can slowly progress to arthritis, myocarditis sometimes with first degree heart block and cranial nerve abnormalities.

The primary defense against Lyme Disease is awareness of the risk and preventing prolonged tick attachment. The insect repellent DEET applied to pants, socks and boots, blousing of pants at the boots and checking for attached ticks when you get back to fire camp are the primary means of prevention. If you have to remove an attached tick it is recommended to grasp the body of the tick with tweezers as close to the skin as possible and pull straight back. Other more traumatic means of tick removal can theoretically increase the risk of infection.

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2. County of Orange Health Care Agency Public Health Bulletin 1999, 49(2):1.
3. Schumacher, MJ, Egen, NB, Significance of Africanized Bees for Public Health, Archives of Internal Medicine 1995, 155:2038.
4. Sherman, RA, What Physicians Should Know About Africanized Honeybees, Western Journal of Medicine 1995, 163:541.
5. Reisman, RE, Insect Stings, New England Journal of Medicine 1994, 331(8):523.
6. Kolocki, P, Delayed Toxic Reaction Following Massive Bee Envenomation, Annals of Emergency Medicine 1999, 33(1):114.
7. Jerrard, DA, ED Management of Insect Stings, American Journal of Emergency Medicine 1996, 14:429.
8. California Environmental Protection Agency, Department of Pesticide Regulation, News Release No. 94-17, 1994.