evidence: Geckos, by nature, don’t carry any venom that’s harmful to dogs. Yet, they may be the hosts of a few different parasites that can cause a lot of damage. [...] Although, that’s not the case. Geckos don’t make any venom, but they do carry a host of parasites and other harmful microorganisms. [...] Are geckos dangerous? Most of the time, geckos are completely harmless to humans and animals.