# Spider Bites — Spider Squad

## The Reality of Spider Bites in Ontario

The vast majority of spider bites in Ontario are not medically significant. Most produce a small welt, localized redness, and mild itching that resolves in 24 to 72 hours without treatment. The reaction is typically to the mechanical puncture and enzyme injection rather than to venom.

Most Ontario spiders bite only when directly handled or compressed against skin (caught in clothing, bedding, or shoes). Spontaneous bites during sleep are much rarer than commonly believed.

## What an Ontario Spider Bite Looks Like

Typical appearance:
- Small red mark at the bite site (one or two puncture marks may be visible)
- Localized swelling, warmth, and redness
- Mild to moderate itching or pain
- Resolves within 1 to 3 days

Bites that warrant medical attention:
- Expanding redness beyond the bite site over 24 to 48 hours (possible infection)
- Central blister or dark discolouration at the bite centre
- Systemic symptoms: muscle cramps, sweating, nausea, difficulty breathing
- Bite in a child, elderly person, or someone with immune compromise
- Any bite causing fever

## Species-Specific Notes

**Wolf spider bite:** Localized pain, redness, swelling. Some itch. Can be more noticeable than house spider bites due to larger fangs. Resolves in 1 to 3 days typically.

**Yellow sac spider bite:** The most clinically notable common Ontario species. Local pain and redness are common. Some individuals develop a necrotic (tissue-damaging) reaction, though this is uncommon. If the bite site darkens, blisters, or shows expanding tissue changes after 24 hours, see a physician.

**Black widow bite (rare in Ontario):** Systemic symptoms — muscle pain and cramps, abdominal cramping, sweating, elevated heart rate, nausea. Bite site itself may be minor. Seek medical attention promptly. Black widow bites are extremely rare in Ontario.

**All other common Ontario spiders (house spider, cellar spider, jumping spider, orb weaver):** Bites are rare and medically insignificant for most people. Minor local reaction.

## What Is Not a Spider Bite

A significant portion of "spider bites" in Ontario are actually bacterial infections (particularly MRSA — methicillin-resistant Staphylococcus aureus), which can produce necrotic wounds that look like severe spider bites. Other causes of skin lesions frequently attributed to spiders: other insect bites, contact dermatitis, folliculitis, and various skin infections.

If a wound is expanding, developing a central dark area, or not improving after 2 to 3 days, see a physician for wound culture to rule out bacterial infection — this is the most likely cause of a necrotic wound in Ontario, not a spider bite.

## What to Tell a Doctor

If seeking medical care for a suspected spider bite:
- Describe where you were and what you may have encountered (gardening, moving boxes, outdoor activity)
- If you caught the spider, bring it in a sealed container — or take a clear photo
- Describe the timeline: when the bite occurred, how the wound has progressed since
- Note any systemic symptoms (fever, muscle cramps, nausea, headache) — these are more clinically important than the local wound

## Prevention

Reduce contact with spiders by:
- Shaking out clothing and shoes that have been on the floor or in storage
- Pulling back bedding before getting in if clothing is stored under the bed
- Wearing gloves when working in wood piles, sheds, or garden debris
- Checking boxes before reaching into them, especially from long-term storage

Professional perimeter treatment reduces spider populations around the home significantly, reducing the chance of indoor encounters. Learn more at spidersquad.ca/spider-control/