Spider Bites

There are approximately 40 – 46,000 described species of spiders in the world. They are capable of crawling in luggage, boxes, duffel bags, fruit crates, etc. and can be dispersed around the world. This does not mean they are necessarily indigenous to an area when found. For example, in Michigan a few years ago, a contractor was bit by a confirmed Brown Recluse. In exploring the history and tracking the materials used for shipping, it was noted lumber was shipped to the building site from Texas. Brown recluse spiders and NOT indigenous in Michigan.

For Survive Outdoors, we are going to stay within North America and focus on the most common spider interactions. It should be noted – There is a large psychological component to spiders and the fear that they generate. Spiders are incredibly beneficial and with more education we can only hope others will not be so quick to resort to the shoe or flyswatter when spotting these amazing creatures.

The vast majority of spiders are carnivorous. They usually have to ensnare their prey and then immobilize before consuming. Venoms of spiders are primarily neurotic and proteolytic peptides with biologic amines. Proteolytic enzymes are also found in some snake venoms. Their primary role is to breakdown protein.

Out of approximately 45,000 spiders, only about a couple dozen are dangerous to humans. Of those couple dozen, only two in the United States are concerning.

Differential Diagnoses of Spider Bites

The most common diagnosis for me, personally, and the patients I have treated over the last forty years are Staph infections or skin abscesses. This also includes MRSA Methicillin Resistant Staph Aureus. These are all too frequently confused with the Brown Recluse bite and at times there is no explanation I can give to convince a patient it is not a spider bite. I mean, saying one has a spider bite is much more exotic and interesting than saying one has a staph infection. Humans cling to this diagnosis and wear it like a badge of courage.

Among the most common differential are: skin abscess, insect bite, herpes, shingles or heroes zoster, allergic dermatitis and plant dermatitis – specifically Hogweed or Cow Parsnip.

Medical History

The patient’s medical history is crucial and can help when formulating a diagnosis.

1. Have they travelled recently?
2. Have they received any packages from out of state? Do they live in an endemic area vs a northern state in reference to the recluse.
3. Time they think they were bit and why? At night vs daytime, In an outside bathroom or privy?  Have they been camping?
4. Where is the bite in relation to their clothes? Is it around the sock edge or on the trunk?
5. If already abscessed, can you culture after you incise?

Treatment of Spider Bites

Specific treatment of spider bites will be addressed for each individual spider we discuss. Please go to specific species: Brown Recluse, Black Widow or Tarantula.

General treatment:

1. Apply cool compresses or Ice. Do not put ice directly on the skin. Use a towel between the ice and wound. This prevents any ice burn to the skin.
2. NO tourniquet. Tourniquets often will exacerbate necrosis of the skin as well as the bite area. Venom from snakes and spiders is dispersed by the time you put a tourniquet on. Numerous studies confirm the tourniquet does not improve outcome.
3. Clean the area well with soap and water or disinfectant.
4. Bacitracin can be used on the bite area to prevent secondary infection like staph or strep. The topical antibiotic will do nothing specifically for the spider bite proper.
5. Observe and watch for expanding redness or tenderness at joints away from the bite. If redness and/or swelling occurs,  this often indicates a secondary infection and you may need an antibiotic.