Category Archives: Medicine

Dangerous animals—spiders

In this installment of the Dangerous Animals series we look at a group that is very misunderstood, and often erroneously indicted for being dangerous—spiders. In the summary chart of dangerous animals, summarized from various sources, spiders are accused of causing 6 deaths a year, on average, in North America. This is more deaths than caused by bears, mountain lions, and wolves combined, and I am highly suspicious of the figure.

In his review of the Centers for Disease Control and Prevention (CDC) data, Langley (2005) summarizes death by all sorts of wild animals, and spider bites have their own classification code, suggesting that the medical community has decided it is worth watching for. For example, the data suggest that between 1991 and 2001 there were 5 fatalities by alligators, and a whopping 66 deaths by spider. People seem to be dropping dead left and right from spider bites. What gives?

In North America, there are two types of spiders known to cause medically significant envenomations in humans: the widows and the recluse. Let’s look at each.

Latrodectus, the Black Widow

Latrodectus, the black widow

Latrodectus, the black widow, showing a characteristic pose, upside down in the web.

There are currently 30 species of spiders within the genus Latrodectus, commonly called widows in North America. The species are distributed world-wide and are on every continent except Antarctica. The venom of the widow contains neurotoxins that inhibit neurotransmission. The spiders like dark and quiet places, with bites occurring when people unintentionally grab or sit on the spider, perhaps under a porch, on lawn furniture, in the tool shed, or in gloves or other item clothing. In the past bites sometimes occurred in outdoor toilets. Symptoms of bites tend to be local and radiating pain, and sometimes back, abdominal, and chest pain, sometimes accompanied by fever, agitation, hypertension, and interestingly, priapism (Vetter and Isbister 2008). People have described it to me like a case of the flu. Untreated, symptoms can last from hours to days. Despite their infamy, death is very uncommon.

Loxosceles reclusa, the Brown Recluse

Loxosceles reclusa, the Brown Recluse

Loxosceles reclusa, a Brown Recluse female guarding her egg sac on a cardboard box in Kansas.

Few spiders generate as much passion and aversion as the brown recluse (Loxosceles reclusa). I currently live in an area where black widows are extremely common, and local people are very casual about them, but are terrified of the brown recluse. I have done many educational programs where I have displayed live spiders, including black widows, and unvaryingly I am treated to several stories by visitors about how they (or someone they know) were bitten by a brown recluse, usually with very bad consequences. (I literally had one person tell me that his aunt had her entire arm removed because of a bite). The thing is brown recluse spiders do not live here! Nothing generates fear like the unknown.

Prior to living where I do now, I lived in an area with gobs of brown recluses, and the people there were generally nonchalant about their presence, as there were almost no cases of bites resulting in horrible wounds.

Distribution map of species within the genus Loxosceles, including Loxosceles reclusa, or the Brown Recluse

Distribution map of species within the genus Loxosceles, including Loxosceles reclusa, or the Brown Recluse (from Vetter 2008).

To be clear, Loxosceles is confirmed to have bitten people and caused wounds that in rare cases take a long time to heal and can leave disfiguring scars, or even death. They are a spider of medical concern. But, having said this, the threat is far over blown.

They are named “recluse” because they like very quite areas, and can frequent homes and storage sheds in quite places. They like corners of basements, and particularly cardboard boxes. Sometimes they crawl into clothing and shoes left on the floor or in the closet. Like with the widows, people are most often bitten when they catch the spider between their body and where the spider is—the bite is defensive.

In a majority of cases, the bite results in local discomfort and nothing more. In some cases a larger wound forms that is tender, but most of these heal with minimal medical intervention, usually within days. Sometimes the wound heals slower, and in rare instances does grow large and can leave a scar. And in very rare cases (<1%) there are more significant systemic issues that can affect major organs and cause death. (Vetter and Isbister 2008).

As mentioned, I lived in an area with known recluse populations. In fact, in one case, 2,055 individual recluse spiders were captured in 6 months from one home in Kansas where the family lived for many years without a single incident attributed to the spiders (Vetter 2008). However, popular perception about these spiders is very different. Why is this?

The most likely explanation is that when the recluse was implicated in bites the most extreme cases got widely reported, heightening awareness in the public and medical community. Diagnoses of recluse bites have become common place, often in areas where the spiders have not been found in the wild, and usually without clear evidence that the symptoms presented were actually caused by a spider, or any other bite for that matter. For example, in Florida, an area without a known population of recluses, during a six year period, 844 brown recluse bites were reported: 124 by medical personnel, 198 by people seeking information about bites, and 522 from people reporting bites treated at a non-healthcare facility (Vetter and Furbee 2006). Physicians are thus occasionally guilty of “practicing Arachnology” by identifying bites, and even spider species, from clinical symptoms alone. The truth is, there are numerous conditions that have been, or could be, misdiagnosed as a recluse bite (Vetter 2008) (see below).

Given the obvious over-diagnosis and misdiagnosis of spider bites, and of recluse bites in particular, I find the assertion that 6 deaths a year in North America are caused by spiders to be highly doubtful. At the very least, this is an undeserved slam against our eight-legged friends, and at worst is misleading the public and medical community, causing potential misdiagnoses and poor treatment choices.

Conditions that have, or could be, misdiagnosed as a bite from a brown recluse (Loxosceles reclusa), from Vetter 2008.


Atypical mycobacteria


– Streptococcus

– Staphylococcus (especially MRSA)

– Lyme borreliosis

– Cutaneous anthrax

– Syphilis

– Gonococcemia

– Ricketsial disease

– Tularemia

Deep Fungal

– Sporotrichosis

– Aspergillosis

– Cryptococcosis

Ecthyma gangrenosum (Pseudomonas aeruginosa)

Parasitic (Leishmaniasis)

Viral (herpes simplex, herpes zoster (shingles))

Vascular occlusive or venous disease

Antiphospholipid-antibody syndrome

Livedoid vasculopathy

Small-vessel occlusive arterial disease

Venous statis ulcer

Necrotising vasculitis

Leukocytoclastic vaculitis

Polyarteritis nodosa

Takayasu’s arteritis

Wegeners granulomatosis

Neoplastic disease

Leukemia cutis

Lymphoma (e.g., mycosis fungoides)

Primary skin neoplasms (basal cell carcinoma, malignant melanoma, squamous cell carcinoma)

Lymphomatoid papulosis

Topical and Exogenous Causes

Burns (chemical, thermal)

Toxic plant dermatitis (poison ivy, poison oak)

Factitious injury (i.e., self-induced)

Pressure ulcers (i.e., bed sores)

Other arthropod bites


Other Conditions

Calcific uremic arteriolopathy


Diabetic ulcer

Langerhans’-cell histiocytosis

Pemphigus vegetans

Pyoderma gangrenosum

Septic embolism

Related posts:
See the rest of the Dangerous Animals series
Pesky house bugs–bed bugs


Langley, R. L. 2005. Animal-related fatalities in the United States–an update. Wilderness & Environmental Medicine 16:67-74.

Vetter, R. S. 2008. Spiders of the genus Loxosceles (Araneae, Sicariidae): a review of biological, medical and psychological aspects regarding envenomations. The Journal of Arachnology 36:150-163.

Vetter, R. S., and R. B. Furbee. 2006. Caveats in interpreting poison control centre data in spider bite epidemiology studies. Public Health 120:179-181.

Vetter, R. S., and G. K. Isbister. 2008. Medical aspects of spider bites. Annual Review of Entomology 53:409-429.

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Is the Carbon Air Purifier Safe?

Air purifiers serve as our shield from many harmful airborne contaminants that may pose health risks. There are different processes with varying degrees of effectiveness since each process or technique can remove specific contaminants in the air.  These processes or techniques include Ultraviolet Germicidal Irradiation, HEPA Filters, Photocatalytic Oxidation, Titanium Dioxide, Ozone generators, Ionizers and activated carbon. These processes when combined together are especially effective. Here, we can take a closer look at a specific process called “activated carbon. “

The carbon air purifier is a technology that treats carbon atoms with oxygen which creates millions of tiny pores between each carbon atom. Adsorption is a process where chemicals are drawn to activated carbon and then bond to it. The millions of pores of activated carbon then provide a massive surface area to trap harmful chemicals in the air. Activated carbon can be thought of like a sponge, the bigger the filter, the more chemicals it can adsorb. Because of this adsorption property, so far, this carbon filters are considered the best filtration system available in the market. It can work well under extreme and varying temperatures. Carbon filters cost approximately $500.00 to $900.00 in the market depending on the model, additional features, and the manufacturer.

Consumers are often concerned with health risks. Is the carbon air purifier safe? There is no reason to worry. In fact, its filters remove many VOCs (Volatile Organic Compounds), Alcohols, Ketones, Halogens, Esters, Ethers, common human and animal odors and other chemicals in the air.  However, these filters are not widely used in households because they do not capture allergens, dust and other micro organisms, so they are not effective for those who suffer allergies, asthma and other respiratory illnesses. Medical practitioners, on the other hand, use this technology for some human applications such as using activated carbon in colon cleansing and to counter ingested toxins because of its adsorbent property. It is also known for adsorbing water impurities.

Purifiers impregnated with activated carbon are recommended for any establishment, but of course remember that not all contaminants are covered by carbon filters, so it is best to combine processes altogether for guaranteed results. Furthermore, activated carbon is safe and used by in industry and medicine regularly.

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The IQair Compact Solution

The IQair compact solution is considered a leading supplier in the air cleaning business backed up by science, quality and excellence. The company’s reputation and dedication on improving the air we breathe started way back in 1963.

IQair has a line of products to choose from which is known for both its technical and stylish design aspects. Its Swiss design is unparalleled. IQair provides homes and businesses with quality air cleaning performance. The performance of the Iqair system was tested and proved during the SARS (Severe Acute Respiratory Syndrome) outbreak which placed them on top after proving that their product could clean the air in hospitals. The technology is also tested by the American Lung Association and recommends it as a superior room purification system. Technically, this product is superior because it purifies the air that passes through the filter to 90% or better.

The IqAir product line includes models such as: HealthPro Compact, HealthPro, HealthPro Plus, GC AM, GC VOC, GC Chemisorber and GC Multigas that carries 1-5 years of warranty along with it after purchase. The HealthPro line specifically has the ideal airflow quality for those people suffering from allergies and asthma.  GC series on the other hand, addresses a specific range of chemicals, pollutants, gases and odors in the air. It is important to determine what your specific air purification requirements are before selecting a system. For example, the IQair 16 will guarantee you the cleanest air possible. It eliminates allergens, dusts and many other viruses and pollutants. For commercial use, IQair HealthPro Plus is recommended for hospitals and other medical establishments where many airborne viruses are present, it is also recommended for household use. The GC Multigas is effective in removing harmful tobacco smoke.

Once again, it is advisable to consider your specific needs before selecting an air purifier system. At the end of the day, an educated consumer can make a wise selection and also provide feedback to manufacturers. This feedback is valuable because it leads to future product improvements and we all benefit from cleaner air to breathe.

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Pesky house bugs—bedbugs

“Sleep tight, and don’t let the bedbug bite,” was a common saying when I was a kid, but I did not really understand it. What was a bedbug anyway? I thankfully went through most of my life without knowing because they were largely eradicated as pests throughout the developed world. However, since the 1990s they have been on the rise.

Bedbugs are parasitic insects in the true bug order Hemiptera. Like other true bugs, they have piercing mouthparts, but unlike most other bugs, bedbugs use them to pierce you and suck your blood. While feeding, the bedbug injects its victim with an anticoagulant saliva. They can live for long periods between meals, but prefer to feed once every five to ten days.

Bedbug nymph

Bedbug nymph

The adult bedbugs are large enough to be easily seen. They are about 1/8 of an inch long and dark brown in color. Their bodies are rounded and flattened front to back. Younger nymphs are small and clear. Bedbugs live in large groups, usually close to their food source, and with a food source their numbers can balloon very quickly. They can be easily transported on clothing, luggage, or furniture and in this way are easily spread from place to place. Infestations can be very hard to detect and eradicate. In recent years dogs have been trained to detect infestations and can do so much faster than a human exterminator in most cases.

Signs of bedbugs include blood spots on the bedding, molted skins of the bugs themselves, clusters of droppings, and the bugs themselves hiding in mattress folds or in the box springs. There is still a stigma about infestations as many people assume that an infestation means the home is unclean, and this stigma means that infestations may not be reported. Hotels increasingly have issues as they serve many people from all over, and once infested, the travelers can carry the bugs home.

Bedbugs feed mostly at night, and they will attack any exposed skin. Bites are not felt at the time, and after feeding for about 10 minutes the bug goes back to hiding. Later, the bites might welt and itch. Sometimes they occur in a line of bites, and are often mistaken for bites from other insects like fleas or mosquitoes, or some other skin rash. This is one reason that infestations can persist for long periods without detection.

You do not have to live with bedbugs however. Getting rid of an infestation is generally not easy, and usually involves a professional exterminator. All areas where the bugs occur should be cleaned and vacuumed. Clothing and bedding should be washed to kill eggs and larva. The bugs will live on mattresses and box springs, behind headboards and in furniture, behind picture frames, and in crevices like around baseboards. Clearing up clutter around the bed is also a good idea. Getting to all the areas where the bugs could be hiding is very difficult. An exterminator will spray insecticides which should be used only as needed since they will be applied to bedding and carpets that you come in contact with too. There is evidence that the bugs are becoming resistant to common insecticides, which is a source of concern.

Be aware. Early detection helps keep infestations from becoming more difficult to deal with. These days more people understand the meaning of “don’t let the bedbugs bite” as these pesky house bugs make a comeback.

A good reference with lots of photos can be found at Also check out the story on Fresh Air.

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Venom, Poison, and Toxicity

There is a great deal of confusion about the terms venom, poison, and toxicity, and they are often used in an imprecise manner. However, the subject is great fun, so let’s explore it a bit.

First, we should clear up the difference between venom and poison. Venom is a substance that is generally injected, such as through a bite. Poison is something that is ingested, such as by eating or inhaling. So, these words relate to how the substance is gotten from point A to point B. Therefore, it is not correct to describe a snake as poisonous, unless it caused you some reaction if you ate it (beyond the thought of eating a snake, that is).

Dance Macabre

Dance Macabre

Monarch Butterflies, on the other hand, are poisonous. They take up toxic substances from the food source of the caterpillars, the milkweed plants, and by concentrating the toxins in their body, they become poisonous to consume. This is a defensive mechanism, not so much for the individual, but for the species as a whole. Any single individual might get eaten, but the effect on the eater is hoped to be so unpleasant as to cause it to not want to eat another one, so the entire species benefits.

Toxicity refers more to the effects of poison or venom. It is a descriptive term used to characterize the medical impact. So, venom can be more or less toxic and still be venom. All spiders are venomous (that is, they inject a venom), but not all spiders are equally toxic, and therefore dangerous, to people.

And, not to put too fine an edge on it, there are things that are toxic without being venom or poison. If you save up a bunch of your saliva, and then loaded it into a syringe and injected it into your skin, you would find that it has a toxic effect on the injection site. That is, the proteins in the saliva would begin to act upon the proteins in your tissues, but we hardly consider humans venomous.

Venom is found throughout the animal kingdom and serves a wide variety of purposes. Some of the most dangerous animals are venomous. Venom can help secure food, as in wasps that sting their victims to lay eggs upon for feeding the larva, or in shrews that bite their prey and inject venom to help immobilize it. Spiders, too, inject venom, which helps immobilize and kill they prey, but it also begins the digestive process so the spider can feed upon the liquefied remains.

Venom can be defensive. For example, a colony of honey bees does not need venom to feed, but uses it as a deterrent to would-be intruders on the hive. Fish, such as the lionfish, have spines with venom that can be injected into attackers upon being bitten. And the male duckbilled platypus has a spin on its hind legs that can inject venom, used again rival males in courtship combat.

Snakes are some of the best known, and most misunderstood, of the venomous animals, and snake venom is diverse in its function and toxicity. In general, snake venom falls into two broad categories: hemotoxic and neurotoxic, but in reality, most snakes have components of both.

Hemotoxic means that the components in the venom attack tissues, like in the spider example, such that the venom is breaking down the tissues of the victim in a pre-digestion process. Such venom can cause extensive damage to tissues, great pain, and cause death slowly over a period of time.

Neurotoxic venoms act upon the nerves system, disrupting the ability of the nerves to send and receive messages. The effect of this kind of venom is that critical nervous system signals stop, such as the signal to your lungs to breath, or to your heart to beat. This kind of venom can act very quickly to cause death.

The vipers, the rattlesnakes, copperheads, cottonmouth in North America, have venom that is mostly hemotoxic, with lesser amount of neurotoxic components. The elapids, the coral snake in North America, and its relatives like the cobras, have venom that is mostly neurotoxic.

So now you can be erudite at parties when friends say things like “Watch out, that black widow you are about to sit on it poisonous!” You can smile politely as you sit, and say “Actually, it is venomous. Let me tell you all about it.”

Related posts:
Venomous snakebites

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