What is the recommended initial treatment and when should urgent medical care be sought for a spider bite, including management of potentially dangerous species such as black‑widow or brown‑recluse?

Spider Bite Treatment

Immediate First Aid

For most spider bites, treatment consists of thorough wound irrigation, ice application for pain relief, over-the-counter analgesics, and watchful waiting—antibiotics are NOT needed initially unless clear signs of infection develop. 1, 2

Essential First Steps

• Irrigate the wound thoroughly with copious warm or room temperature water until no foreign matter remains 1, 2
• Apply ice with a clean barrier between ice and skin for local pain relief 1, 2
• Remove rings and constricting objects immediately from the affected extremity, as swelling may occur 1, 2
• Elevate the affected area to reduce swelling and accelerate healing 2
• Apply antibiotic ointment and cover with a clean occlusive dressing to improve healing and reduce infection risk 1, 2

Pain Management

• Use over-the-counter acetaminophen or NSAIDs for pain control 1, 2
• Apply topical lidocaine 5% if skin is intact for additional pain relief 2
• Oral antihistamines can reduce itching and swelling 2

Critical Pitfall: Antibiotics Are Usually NOT Indicated

Swelling in the first 24-48 hours is caused by allergic inflammation, NOT infection—do not start antibiotics prophylactically. 2 Universal prophylaxis with antibiotics is not recommended for bite wounds. 2 The common mistake is assuming antibiotics are needed for swelling around the bite site, when swelling is typically caused by mediator release, not infection. 1

What NOT to Do

• Do not apply suction to the bite site—it is ineffective and potentially harmful 1, 2
• Do not apply tourniquets or pressure immobilization bandages—they may worsen tissue injury 1, 2
• Do not close infected wounds 2

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When to Seek URGENT Medical Care

Immediate Emergency (Call 911)

Seek emergency care immediately if ANY systemic symptoms develop:

• Difficulty breathing, bronchospasm, or laryngospasm 2
• Muscle rigidity or severe muscle cramping 1, 2
• Dizziness, confusion, or altered mental status 1, 2
• Rapidly progressive swelling involving face, lips, tongue, or throat (angioedema) 2
• Syncope or hypotension 2

Urgent Medical Evaluation Needed

• Pain extending beyond the bite site or becoming severe 1, 2
• Pain not controlled by over-the-counter medications 1, 2
• Open wound develops 1, 2
• Signs of secondary bacterial infection appear (see below) 1, 2

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When Antibiotics ARE Indicated

Antibiotics should only be started when clear signs of secondary bacterial infection develop:

• Progressive erythema extending beyond the initial bite site 2
• Purulent discharge from the wound 2
• Systemic signs of infection such as fever or elevated white blood cell count 2

Antibiotic Selection for Confirmed Infection

• First-line oral therapy: Trimethoprim-sulfamethoxazole or doxycycline to cover MRSA 2
• Alternative option: Clindamycin, if local resistance patterns permit 2

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Management of Dangerous Species

Black Widow Spider Bites

Black widow bites produce minimal skin changes but cause severe neuromuscular symptoms including muscle cramping, pain, and potential respiratory paralysis. 3, 4

Symptoms and Presentation

• Sharp pain at bite site (similar to needle puncture) occurring 15 minutes to several hours after bite 3
• Ascending motor paralysis with muscle cramps beginning in thigh, shoulder, and back 3
• Boardlike abdominal rigidity with minimal tenderness 3
• Feeble pulse, cold clammy skin, labored breathing, restlessness, and anxiety 3
• Symptoms increase in severity for several hours to a day, then slowly resolve over 2-3 days 3

Treatment Approach

• Hospitalization is recommended 3
• Prolonged warm baths provide greatest relief 3
• Intravenous calcium gluconate 10 mL of 10% solution repeated as necessary to control muscle pain 3, 4
• Morphine may be required for pain control, but use cautiously as venom causes neurotoxicity and potential respiratory paralysis 3
• Muscle relaxants for symptom control 3, 4
• Antivenin (Latrodectus mactans) is available and emphasized for early use for prompt relief, though pain control and muscle relaxants are generally adequate 3, 4
• In otherwise healthy individuals aged 16-60, antivenin use may be deferred in favor of muscle relaxants 3

What NOT to Do for Black Widow Bites

• Do not apply tourniquets 3
• Do not attempt incision and suction—nothing is gained by removing venom from the bite site 3
• Local treatment of the bite site is of no value 3

Brown Recluse Spider Bites

Brown recluse bites cause painful ulcerated wounds that progress over days to weeks, with the primary treatment being rest, ice compresses, and delayed surgical debridement—NOT aggressive medical therapy. 2, 4

Clinical Presentation

• Dermonecrosis develops within 72-96 hours 4
• Central discoloration (81% of cases) and necrosis (37% at presentation) 5
• Systemic loxoscelism is rare but can produce massive hemolysis with minimal skin changes 4
• Most wounds (59%) involve the leg 5

Treatment Approach

The evidence strongly suggests conservative management, as most bites heal with supportive care alone and aggressive therapy does not improve outcomes. 6, 5

• Rest, ice compresses, and supportive care are the mainstay 2, 4
• Antibiotics only if secondary infection develops 4
• Delayed surgical debridement (several weeks after bite) if needed 2, 4
• Avoid systemic corticosteroids and dapsone—these were associated with slower healing and increased scarring in a 5-year study of 189 patients 6

Important Evidence on What NOT to Use

A rigorous 5-year study found that after controlling for bite severity, systemic corticosteroids and dapsone were associated with slower healing and dapsone increased the probability of scarring. 6 Only 3% of patients required skin grafting, and serious complications were rare. 5 This contradicts older recommendations and emphasizes that aggressive medical therapy does not appear warranted. 5

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Expected Recovery Timeline

• Most patients with local symptoms only will recover completely within 24-48 hours 1, 2
• Continue pain management with over-the-counter medications as needed for several days 1, 2
• Follow-up within 24 hours either by phone or office visit is advised 2
• Residual symptoms such as general weakness, tingling, nervousness, and transient muscle spasm may persist for weeks or months after black widow bites 3