Category Archives: Toxicology

Nerve Gas and Tomahawk Missiles

In August 2012 President Obama said “a whole bunch of chemical weapons moving around …that’s a red line for us.” This was in reference to an admission by the Assad regime in Syria that they had chemical weapons but they would “never, never be used against the Syrian people or civilians during this crisis, under any circumstances.” Within a year, there was evidence that suggested that the nerve gas Sarin had been used on a civilian population.

In the U.S, polling showed that the public had tired of war and was on record as opposing more involvement by our military in the area. Obama sought a joint resolution for an “Authorization for the Use of Military Force Against the Government of Syria to Respond to Use of Chemical Weapons.” The resolution failed. With neither public nor congressional support for military action, Obama sought an agreement with Assad to remove the chemical weapons.

After the recent use of Sarin, the current administration acted without congressional approval and launched an attack with 60 Tomahawk missiles on an air base in Syria. It is thought that this was the base from which the most recent chemical attack was launched.

Sarin is a very toxic nerve agent. It actually isn’t a gas but rather a liquid designed to be aerosolized, meaning sprayed as a fine mist. Contact with bare skin or especially inhalation causes a number of symptoms ranging from heavy salivation, profuse sweating, muscle cramps, convulsions and death resulting from respiratory paralysis. Not pretty, huh?

Sarin is a member of a class of poisons known as Acetyl Choline Esterase Inhibitors. Other substances that have the same effect, but lower toxicity are a number of insecticides. Even the relatively safe house and garden type insecticides kill insects by the same mechanism. So how do they work?

Imagine you want to wiggle your big toe. A message travels from your brain via several nerves “talking” to each other to get the signal all the way to your toe. For the signal to get from one nerve to the next requires the opening and then closing of a “gate.” The gate opening allows the signal and the closing stops the signal. If the gate doesn’t close your toe would continue to wiggle. That is the way Sarin and other Acetyl Choline Esterase Inhibitors work. They keep the gate open. A small stimulation of a nerve can’t be turned off. The affected tissue is overstimulated.

Back to the deaths from Sarin in Syria and our military response. By bombing the airfield a message was sent but is seems to be a fairly ineffective one. Within days the base was back in operation and launching conventional bombing attacks on the same town that had been attacked with Sarin. Now we are left with what’s next?

A recent Galllup poll found that a scant 51% supported our missile attack on the airbase, and 54 % oppose any further strikes. Finally, 69% are not confident that the the one strike will dissuade Assad from again using chemical weapons.

Cell Phones and Cancer, Again

Like the Phoenix rising from ashes, so is the “cell phones cause cancer” meme. The current claim is based on a study done with rats exposed full body for nine hours a day for several months. The result was a statistically significant increase in two types of tumors, gliomas and schwannomas. Gliomas are tumors in glial cells of the brain and are rare, the incidence in 2008 was less than 7 per 100,000. In this study the schwannomas were found in heart cells and are even rarer. Important also was the fact that there was a dose-response relationship. Higher intensity cell phone radiation produced a greater incidence of tumors.

So is it time to keep that phone on speaker and never, never carry it around in your bra? Maybe not, at least the bra part. Where as there were increased tumors observed in male rats, there was no increase in tumors in females regardless of the dose (intensity of radiation.) That in itself is a problem as both male and female rats have glial and schwann cells so why were only the males affected?

The bigger problem with a link between cell phones and cancer is the fact that it is biologically implausible. Cell phones utilize radio waves as do WiFi, TV, microwaves and others. This is the lower energy form of electromagnetic radiation that does not cause ionization and therefore doesn’t cause chemical reactions. A chemical reaction is required to cause a mutation in DNA and hence initiate cancer. Higher energy radiation known as ionizing is a well know cause cancer. Too much ultraviolet (UV) radiation from the sun is the most common cause of cancer. X-rays are also a known cause of cancer.

The history of cell phones and cancer is somewhat odd. In 1989 Susan Reynard , 31, was diagnosed with an astrocytoma, a tumor of the astrocytes which is another type of brain cell. The tumor, in the eyes of her husband resembled the outline of a cell phone – just like she held it to her head. She died in 1992 and her husband sued the phone manufacturer and service provider claiming a causal link between her cell phone use and the tumor which killed her. He lost the suit.

A number of studies with laboratory animals and epidemiological studies with humans have been been conducted over the years with variable outcomes. Studies with animals always suffer from the fact that there may be physiological differences between us and other animals, hence risk factors will be different.

Even without a controlled study the connection between brain cancer and cell phone use seems sketchy. Whereas the incidence of brain cancer has remained relatively steady over the past few decades, use of cell phones has increased several hundred fold. It is estimated that 91% of adults in the US use cell phones.

Epidemiological studies look at the relationship between disease and human population factors. The most accurate are prospective studies where a group a people are followed over a long time span to see if there is a correlation with a disease and their exposure. A prospective study concluded in 2011 confirmed this lack of a relationship. Thousands of participants across 13 countries were followed for close to a decade. The was no discernible relationship whatsoever between cell phone use and cancer.


Chemophobia is a term, often used pejoratively, to describe an unfounded and generally unnecessary fear of “chemicals.” The quotes are necessary because anything with physical substance is a chemical. The phobia is really just a fear of the unknown or the not well understood. Concern should be about the risk of exposure to those that may be toxic, mutagenic, or harmful in in some way, not all chemicals.

After that leap, it makes more sense as different chemicals or mixtures thereof have different potentials for harm, and those potentials are directly related to the dose. Paracelsus (1493-1541), the father of modern toxicology, coined the phrase “everything is toxic, nothing is toxic, the dose makes the poison.” We are bombarded daily by toxic and even carcinogenic substances but the vast bulk of these are present in such small amounts, that the toxic or carcinogenic dose is immeasurable and no harm can be detected.

Historically there are lots of substances which one should rightly fear and lot of them are natural. A class of compounds known as cyanogenic glycosides can release deadly hydrogen cyanide. Lima Beans contain these compounds but at low enough concentration to have no toxic effect whatsoever. Cassava, a annual root crop in tropical parts of the world, also contain cyanide. Generally consumption is not a problem, but when consumed as a significant portion of the diet the cyanide intake can be large enough to cause paralysis in the extremities, blindness and even death. It’s OK to eat tapioca pudding made from cassava just don’t try to live on it.

People are more often fearful of synthetic materials, as if they’re some how automatically toxic regardless how much or how little one is exposed to. Modern chemical analysis can now measure substances down to concentrations unheard of just a decade or two ago. Just because a synthetic compound can be measured in the body doesn’t necessarily mean that it is causing any harm.

Another contributing factor to chemophobia is the “one small study” problem. A small study will show the harmful effect of something, then the press runs with that as a confirmed truth. Often however, small studies are just plain wrong. The beauty of science is that over time we usually get it right. Larger, more well controlled studies can disprove the purported harmful effects.

The Food and Drug Administration was created at a time when there was a clear and present danger to our supply of food and drugs. The scientific consensus is that they currently do a commendable job of protecting us from harm.

Ironically on area of real risk comes from so called natural nutritional supplements. An exception in the law prevents these agents from oversight by the FDA. Whereas most nutritional supplements are harmless (and by the way useless), some have been found to be adulterated with dangerous levels of natural and synthetic compounds. Illness and even death have come from these unregulated agents.

Chronic Wasting Disease

Last month Arkansas Game and Fish confirmed that a deer found dead near Ponca, Ar and an elk taken by a hunter were both found to have Chronic Wasting Disease (CWD). This ultimately fatal disease is not yet known to be transmissible to humans who consume the flesh of an infected animal. It is the same disease which showed up in Great Britain years ago, called Mad Cow Disease. In sheep, where the disease has been known for centuries, it is called Scrapie. In the remote highlands of New Guinea, warring tribesmen spread the same disease, known as Kuru, through ritual cannibalism. There is even a heritable form called Creutzfeldt-Jakob Disease (CGD.)

The assemblage of diseases are collectively known as transmissible spongiform encephalopathies (TSE.) What that means is that one may get it from eating the flesh of an infected animal and over time fatally damages the brain. The really unique thing about prion diseases is the nature of the infectious component of disease transmission.

With every other kind of transmissible disease from the common cold to the plague, from warts to ebola, transmission requires an organism such as a bacteria, or at least a virus. These agents replicate by well understood mechanisms involving DNA. Reproduction is necessary to create enough of the organism in a body to do it harm.

Stanley Prusiner won the Nobel Prize in Physiology or Medicine in 1997 for “his discovery of prions – a new biological principle of infection.”

As noted Scrapie has been known for centuries. Sheep farmers knew that the disease could be spread from one animal to another in a herd, although it may take years between infection and the presentation of symptoms in an infected animal. By the 1950s and with an awareness of the modern germ theory of disease, the cause of Scrapie was thought to be a viral. Because it took a long time for symptoms to present it was called a slow virus.

Prusiner began studying the disease in the ’70s. It was known that the disease could be spread from on organism to another via extracts of diseased brains tissue. What Prusiner discovered however was that when these extracts were treated with agents that destroyed DNA and RNA – nothing happened – the extracts were still infectious. This was previously unheard of. At first it was thought that a new kind of life (an organism) that replicated without DNA. Not so.

The infectious agent isn’t an organism, it is a simple molecule that already exists in all of us, quite possibly all multicellular organisms. Prions are proteins. Proteins all have unique three dimensional shapes. Prions are nothing more than a misshapen protein, except their misshapen form causes normally shaped protein to become similarly misshapen. The “bad” form catalyzes the change from the normal to the bad shape. Brain tissue riddled with the badly shaped protein take on a sponge-like appearance, with the loss of normal brain function.

The protein is found not only in brain tissue but virtually all nervous tissue. Consumption of any flesh of an infected animal, even an asymptomatic one carries a risk of contracting a lethal disease. Thorough cooking which normally destroys the usual infectious agents may not suffice to destroy the prion.

Get the Lead (Pb) Out.

Professor Plum – did it in the kitchen – with the lead pipe. This could have been an outcome in the old board game, Clue. In reality and recent times it was the the emergency manager in Flint Michigan, with the lead pipes in the cities antiquated distribution lines.

Back to Flint, Michigan later, but first a brief history and discussion of the toxic nature of lead. Lead is the quintessential example of the class of elements know as heavy metals. Other toxic heavy metals include Mercury and Cadmium. Heavy metals generally share a capacity to cause nerve damage in both peripheral and central nervous systems. The element symbol, Pb, comes from the Latin Plumbum, which is also the root of the English words plumber, and plumb-line.

Lead has been in common use for centuries. Lead glaze in pottery has been dated to circa 4000 BCE in Egypt. It is a dense, relatively non oxidizing (won’t “rust” like iron) malleable material. Among its many uses are jewelry, solder, lead pipes, batteries, and of course the most toxic form-bullets. In various chemical combinations it has been used as durable paint pigment, and an anti-knock agent for gasoline. In ancient Rome a chemical compound of lead was used to sweeten wine. Not surprisingly the compound’s common name is sugar of lead, made by dissolving lead in vinegar to get lead acetate.

Lead came into use about the time of the iron age, but may have preceded iron as it is easier to smelt from its ore, Galena. It’s toxicity has also been known from ancient times. Acute lead poisoning is rare, but chronic poisoning was common. The forerunners of modern chemists were the alchemists. They for reasons know only to them associated some elements with planets. Lead was connected to Saturn. The word saturnine is an adjective meaning slow, gloomy, taciturn, even cynical. These describe nicely the early symptoms of lead poisoning. Further progression of poisoning involves damaged memory, confusion, and tremors. Some of these symptoms can be irreversible.

Chronic lead poisoning is at its most insidious when children are involved. If items with any lead content are in the presence of a toddler, it will likely end up in the child’s mouth. Lead based paint was common, and the toxicity known since early in the 20th century. A painted window sill is the perfect spot for a teething toddler. Regulation of the industry was resisted for decades, the industry blamed the parents for not keeping toys, window sills, etc out of the mouths of children.

The most recent example of lead poisoning in children takes us back to Flint, Michigan. The collapse of the auto industry and other financial troubles lead the state to take over management of the city. An emergency manager with broad authority to manage the city budget caused (or allowed) the city to switch their water supplier from properly treated Lake Huron water to untreated water from the Flint river. This untreated water flowed through the city’s lead pipe distribution system. Proper treatment can prevent leaching, but it wasn’t done. Subsequently as many as 10,000 children have been identified as having toxic levels of lead in their blood. Many could suffer permanent kidney, liver, and brain damage.

Lethal Laetrile

In 2013 the parents of a 2 year old girl abandoned traditional medicine in Maine and sought a alternative healer in Arizona for treatment of a form of eye cancer. This was against the recommendations of the physicians in Maine who had determined that the cancer had spread to the surrounding tissue and needed additional conventional treatment.

The alternative healer, Martha Grout MD, didn’t use traditional treatment for the condition, a known protocol but rather substituted the use of Laetrile, which has never been shown to be a treatment for any condition, much less cancer, and is not approved for use by the Food and Drug Administration.

The drug was administered by the doctor at about 3 PM and the child was dead by 8. Cause of death? Cyanide poisoning. The doctor was reprimanded but not prosecuted and continues to practice her particular voodoo.



Laetrile, aka Amygdalin, is made from the seeds of the Rosaceae family and contains a substance which when consumed releases cyanide, in this case a lethal dose. So much for safety of this “natural medicine.”

Laetrile has been around since the 1950s but has never been shown to be effective in treating any condition. The original proponents suggested that normal cells can’t cause the release of cyanide, only cancer cells could. Cyanide would only be released within a cancer cell, killing it, but sparing normal cells. Not true.

Steve McQueen, the actor known for motorcycle chases in a World War II movie or a car chase movie in San Francisco, died while receiving Laetrile treatments in a clinic in Mexico in 1968. Laetrile can still be obtained from Mexico.

When the FDA began seeking fraud prosecutions for those selling Laetrile, the story changed. It was then described as a vitamin (Vitamin B-17), a deficiency of which could lead to cancer. This tack was taken because vitamins are regulated differently than drugs. Again the problem is that it is just not true. Laetrile is not a vitamin. There is know known condition that results from not having Laetrile as part of any diet.

Yet again the story changed. Once it could no longer be legally marketed as a vitamin, it became a necessary ingredient in a holistic approach to complete health, what ever that means.

Today the field of quackery is wide open due in large part to the internet and a significant change in the law with respect to how drugs are regulated. Previously anything sold as a drug had to be proven both safe and efficacious. In 1994 Senator Hatch of Utah sought and had enacted the Dietary Supplement and Health Education Act.

Basically it defined a new class of “drugs” known as dietary supplements that no longer required proof of effectiveness or even safety. The only protection a consumer has is that the substance is what it claims to be, and doesn’t claim to be a drug. Advertizing is rife with claims such “supports a healthy” or “contributes to” or “promotes.” These terms can be interpreted by consumers as a supplement may really do something, but are sufficiently vague that they escape any regulation as a real drug.

Now more than ever – caveat emptor – let the buyer beware.


Mercury in the Evironment

A human body contains on average 3 grams of Mercury (Hg), in the form of dental amalgam. Cremation releases the material to the atmosphere in the form of gaseous elemental Mercury. As Mercury is a well known toxin, should there be concern over its release to the environment via cremation?

Currently there are over a million cremations a year in the United States, resulting in the release of about three tons of Mercury. That is a lot of Mercury but it pales in comparison to the Mercury released from burning coal – over 50 tons per year.

Just how dangerous Mercury exposure is depends on two important variables, the chemical form and the amount of the exposure (dose). In the elemental form, for example the liquid in older thermometers, it has a relatively low acute toxicity. If inhaled in the gaseous form or absorbed through the skin in the liquid form it is poorly metabolized and rapidly excreted unchanged. We are all exposed to trace amounts of elemental mercury from airborne sources, but in this form it presents little hazard.

Even children on a playground near a crematorium are at little to no risk from this type of Mercury. This doesn’t mean that the Mercury from a crematorium is of no consequence, but the explanation is more complex.

Mercury in the form of a salt is much more toxic. Lewis Carroll’s Mad Hatter of Alice in Wonderland was a parody of the real life risk of hatters of the 19th century. Exposure to certain Mercury salts caused tremors and a form of dementia.

The Mad Hatter

The Mad Hatter

Hat makers in Central Asia used felt which was obtained by separating the fir from the skin of small animals. Traditionally camel urine was used to help form the felt. When felt preparation moved to Europe, hatters substituted their own urine. It was soon discovered that hatters who had syphilis and were being treated with Mercury salts made better felt! Thenceforth, solutions of Mercury salts were substituted for urine for hat making.

The most toxic form of Mercury comes in the form of certain organomercurials, specifically Methylmercury. In this form it is easily absorbed, where it binds to and destroys nervous tissue. This is the form of Mercury found in both fresh and saltwater fish.



The first recognition of the toxicity (principally nerve damage) of Methylmercury occurred in Japan in 1956 and was referred to eponymously as Minamata Disease. Chisso Chemical Company on Minamata Bay manufactured industrial chemicals and disposed of their wastes in the bay. A component of the waste was Methylmercury which was absorbed by fish and shellfish. Consumption of the sea food resulted in chronic poisoning and thousands of deaths.

This brings us back to the crematorium and the release of the relatively non-toxic elemental Mercury. When this mercury is deposited on soil or in water, it makes its way to the benthic layer – basically the mud at the bottom – of streams and lakes. There, anaerobic bacteria convert it to the much more toxic Methylmercury. It bioaccumulates in the smallest organisms, then up the food chain to fish.

The long and short of it is that it is not a good idea to allow release Mercury to the environment. The problem is easily solved however by simply removing the Mercury amalgam from teeth before cremation, as has been proposed by Humphrey Funeral Service. They are currently seeking a permit to construct a crematorium near Center Valley here in Pope County. If so they will be the first in the nation to take this simple but environmentally important step. Occam’s razor, don’t operate a crematorium without it.


Arsenic Anyone?

A popular talk show doctor recently had several brands of Apple juice tested and claimed to have found Arsenic. Whereas nobody wants poison in her food, the question of the amount and its relevance is important. First a little background on Arsenic.

One of the first things that come to mind in association with Arsenic is poison. And indeed it is poisonous. It has been used as a pesticide because it is generally poisonous to all forms of life, rats, cockroaches, even some fungi succumb to it. Ironically it is also known to be an essential trace element for some organisms and possibly humans in tiny, tiny amounts.
Arsenic has been known since antiquity and is poisonous to varying degrees depending on its form. As important as the potency of a poison is the amount of the poison. A seventeenth century physician-chemist by the name of Paracelsus famously proclaimed “everything is poisonous, nothing is poisonous, the dose makes the poison”. One example is lima beans which naturally contain toxic cyanide ion, but lima beans aren’t toxic as the dose of cyanide is too small.
Arsenic has historically been a component of intrigue. In 15th century Italy the Borgia family waxed powerful. Lucrezia and Cesare were among the children of Cardinal Rodrigo Borgia (who became Pope Alexander VI- obviously things in the church were different in those days!) Lucrezia was said to be a very effective poisoner as she had learned how to concoct lethal Arsenic potions which were undetectable in food or drink. Arsenic-laden wallpaper
Napoleon may have been done in by Arsenic, but not by an intentional poisoning. His villa on the island of St Helena had wallpaper colored with Sheele’s Green, a pigment made from Arsenic. In moist air a mold can grow on the wallpaper and convert the Arsenic to a volatile form. It appears at least for Napoleon that not the butler but rather the wallpaper did it. Another Arsenic pigment called Emerald Green may have impaired the health of Cezanne, Van Gogh, and Monet among others.

Emerald Green Paint Pigment

Emerald Green Paint Pigment

Some women in the Victorian era would eat small amounts of Arsenic to produce a pale complexion. Tanned skin in those days indicated that one worked in the fields and was therefore of a lower class.
Now back to Apple juice. Any Arsenic in juice is an issue if for no other reason that juice is a mainstay of many children. Two questions come to mind. Where did the arsenic come from and is there enough Arsenic in the right form to be a risk to health?

 Generally speaking the Arsenic is coming from the soil in which the fruit is grown. It can be in the soil naturally or due to use of Arsenical pesticides applied to the soil. Lead Arsenate was used in the United States until the seventies. Arsenic is very stable and could persist in soils for many years. Another source may be China, where environmental regulations are lax at best. Over half of the Apple juice sold in the United States now comes from China.

The amount of Arsenic measured recently in some of the juice samples does exceed the World Health Organisation’s suggested limit for safety. However the method of measurement included both toxic inorganic and relatively nontoxic organic Arsenic. When only the toxic form is considered the level appears to be safe. The FDA has been monitoring arsenic in Apple juice for decades and sees no threat to public safety based on these findings.


Worried Sick- the Nocebo Effect

A synthetic form of thyroxine called Eltroxin, chemically and biologically identical to natural thyroxine, has been in use for over forty years. It is used effectively to treat hypothyroidism which if left untreated can result in a range of symptoms up to and including heart disease. In 2007 GlaxoSmithKline moved its manufacture from Canada to Germany. At the same time they updated the actual tablet, changing its physical form but leaving the active ingredient the same.

Shortly thereafter in New Zealand a trickle of reports of adverse side effects not seen before were received by a health monitoring organization. After the new side effects began to show up in the press, reports of the new symptoms skyrocketed over a thousand fold even though the only difference was the appearance of the pills, not the chemistry.

A study by a team of Italian gastroenterologists involved patients who were lactose intolerant and a control group who weren’t. The subjects were told that the study involved examining the effects of lactose on the gut. Even though the subjects were given only a glucose tablet which can not cause symptoms, forty four percent of those intolerant and and 26 percent of those tolerant, reported gastrointestinal problems.

Many here in the US and overseas suffer from a so called WiFi syndrome. A range of symptoms including nausea, head aches, joint pain etc. occur when they know they are exposed to electromagnetic fields, but only if they know they are exposed. There is absolutely no evidence that the EMF can cause these symptoms.

These examples are only three of hundreds of examples of what is know as the nocebo effect, from latin for “I shall harm”. In years past this may have been referred to as a form of mass hysteria, now more benignly called a psychogenic illness. In some cases it has been shown that the mere suggestion of a possible symptom or side effect can cause a biochemical change in the body which results in the symptom, but only from the suggestion.

This was shown elegantly in an animal model using rats. They were trained by classical Pavlovian training to become asthmatic. First the experimenters gave the rats a natural substance, histamine, which causes an asthma reaction and paired that with the ringing of a bell. In subsequent trials just the bell ringing would cause the rats to release excess histamine into their blood, thus triggering an asthma attack. If rats can be trained to become asthmatic, shouldn’t it be true that people who have asthma reactions could be trained to not react?

The nocebo effect is the evil twin of the better known placebo effect, latin for “I shall please”.

nocebo and placebo

nocebo and placebo

Any benefits of homeopathic medicine, and much folk medicine are a result of the placebo effect, including modern day agents associated with Traditional Chinese Medicine, acupuncture, much of chiropractic, and over the counter medications called nutritional supplements.

The question as to whether society should allow profit from the sale of placebos is a moral one. Should some one make money by suggesting that a nostrum will do something, even if it only works for believers? It sure works for Madison Avenue. Ca-ching.

poison ivy

Poison Ivy

The old adage “leaves of three, let it be” helps to identify and therefore avoid poison ivy. The plant is polymorphic, growing as ground cover, small shrubs up to two or three feet high, or a climbing vine. It is often confused with virginia creeper which has five leaves. Formally named Toxicodendron radicans, it and other related plants contain urushiol (oo-rush-ee-ol) . The substance is present in all parts of the plant; leaves, stems, roots, and berries. Poison ivy, poison oak, and poison sumac are known to cause the characteristic itchy, blistering rash.



Other plants such as cashews also have urushiol when raw and must be properly processed, shelled and roasted, to remove the plant oil. Lacquer, the stuff that produces the beautiful shiny finish in furniture, contains small amounts of urushiol and can affect hypersensitive individuals. The name urushiol comes from the Japanese name for Lacquer, urushi.

The first time, or first few times one is exposed there usually isn’t a reaction. Only after being exposed does one become sensitized and on second exposure develop the itchy rash. This is because urushiol is an allergen, something which causes an allergic reaction , and and the allergy has to be “learned” by exposure.

Actually it is a bit more complex. Only proteins, very large molecules, can cause an allergic reaction. Much of our bodies are protein so our immune system must be able to distinguish our proteins and foreign proteins. Antibodies develop as a method to rid the body of foreign protein. A whole cascade of chemical reactions occur once the immune system identifies a foreign protein. Urushiol is not a protein but a substance know as a hapten. Haptens are small molecules which can chemically react with protein. Once a protein, for example the keratin of our skin, has reacted reacted with urushiol our bodies no longer recognize the protein as “self” but rather as foreign.

Urushiol is a fat soluble oleoresin, which means that it can penetrate the skin within an hour or two. There it reacts, “labels” the protein, and sets the allergic reaction in motion, the rash occurring several hours after exposure. Heavier exposures result in a faster reaction.

This has lead to the misconception that the allergen may be carried through the blood. For example heavy exposure to the back of the hand and only slight exposure to the upper arm means that the rash will show up on the hand first and arm only later.

Another misconception is that the fluid present in the blisters contains the poison. Once the blisters form, the poison is long gone. You can’t get a reaction just by coming in contact with someone else’s rash. You can be exposed by secondary contact however. There is a fairly wide variation is sensitivity so exposure and subsequent reaction can occur when a sensitive person handles the clothes of a less sensitive person.

In extreme cases, people are exposed by inhaling smoke particulates from burning poison ivy. This can be dangerous as the rash occurs in the throat and even in the lungs.