From the Guidelines
Antibiotics are not typically needed for most spider bites, and their use should be reserved for cases with clear signs of infection. When considering the management of spider bites, it's essential to prioritize the prevention of infection and promote healing. According to the 2024 American Heart Association and American Red Cross guidelines for first aid 1, the primary approach to spider bites involves localized wound care and over-the-counter analgesics for pain.
For common spider bites that become infected, oral antibiotics like cephalexin (500 mg four times daily for 7-10 days) or dicloxacillin (500 mg four times daily for 7-10 days) may be prescribed, as these target the most common skin bacteria like Staphylococcus and Streptococcus. Key considerations for the use of antibiotics include:
- Increasing redness
- Warmth
- Swelling
- Pus
- Red streaking from the bite
Most spider bites heal on their own with basic wound care, including:
- Cleaning with soap and water
- Applying antibiotic ointment
- Using cold compresses to reduce swelling
It's crucial to seek immediate medical attention for severe bites from brown recluse or black widow spiders, as these may require specialized treatments beyond antibiotics. The decision to use antibiotics should be made by a healthcare provider after examining the bite, as unnecessary antibiotic use contributes to antibiotic resistance and may cause side effects without providing benefit 1.
From the Research
Antibiotic Treatment for Spider Bites
- There is limited information available on the use of antibiotics for spider bites specifically 2, 3, 4, 5.
- Most spider bites cause minor effects and do not require antibiotic treatment 3, 4, 5.
- However, some spider bites can cause significant morbidity and rarely, mortality, and may require medical attention 3, 4, 5.
- The use of antibiotics for spider bites is not well-studied, but a study on human bites suggests that low-risk bites may not require antibiotic treatment 6.
- It is essential to note that spider bites are often difficult to diagnose, and the decision to use antibiotics should be made on a case-by-case basis, considering the severity of the bite and the patient's overall health 4, 5.
Considerations for Antibiotic Use
- The majority of suspected spider bites present as skin lesions or necrotic ulcers, where the history of a spider bite must be confirmed 5.
- Important groups of spiders worldwide include the widow spiders, recluse spiders, and some mygalomorph spiders, which can cause significant effects 3, 4, 5.
- Clinicians must consider spider bite in the differential diagnosis of unexplained autonomic and neurological dysfunction, particularly in children 3.
- In Australia, skin ulceration is more likely to be an infective, inflammatory, or traumatic cause than a case of necrotising arachnidism 3.