Dry bites
In at least 20% of pit viper bites and a greater percentage of elapid and sea snake bites, no venom is injected .
Local features
Fang marks: Generally, the presence of two puncture wounds indicates a bite by a poisonous snake. In the case of a non-venomous snakebite, small puncture wounds are seen arranged in an arc.
Pain : Burning, bursting or throbbing pain may develop immediately after the bite and spread proximally up the bitten limb. Draining lymph nodes soon become painful. Krait and sea snake bites maybe virtually painless.
Local swelling : Viper bites produce more intense local reaction than other snakes. Swelling may become apparent within 15 minutes and becomes massive in 2-3 days. It may persist for up to 3 weeks. The swelling spreads rapidly from the site of the bite and may involve the whole limb and adjacent trunk. Regional lymphadenopathy may develop. In case the envenomed tissue is contained in a tight fascial compartment like the pulp space of digits or anterior tibial compartment, ischaemia will develop. If there is no swelling 2 hours after a viper bite, it is safe to assume that there has been no envenoming .
Local necrosis: In viper bites, bruising, blistering and necrosis may appear over few days following the bite. Necrosis is marked following bites of Asian pit vipers, and some rattlesnakes. Bites by Asian cobras can also cause tender local swelling and blistering. Krait bites usually do not cause any local reaction. Patients spat at by spitting elapids may develop venom ophthalmia.
Secondary infection: Bacterial flora in the oral cavity of the snakes contributes to secondary infection.
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