The vast majority of small house lizards encountered in residential areas, most commonly the common house gecko (Hemidactylus frenatus), are entirely harmless to humans. This species is found globally in tropical and subtropical climates and is neither poisonous nor venomous. Concerns about toxicity are unfounded, as these small reptiles pose no threat from a bite or skin contact.
The Definitive Answer: Poisonous vs. Venomous
Confusion regarding the safety of house lizards often stems from misunderstanding the biological difference between “poisonous” and “venomous.” A poisonous animal contains toxins absorbed when touched or ingested. In contrast, a venomous animal injects toxins into another organism, usually through a bite or sting.
House geckos do not produce toxins, meaning they are neither poisonous nor venomous. They lack the specialized glands and delivery systems, such as fangs or stingers, required to inject venom. If a gecko bites—which only happens if severely threatened or handled roughly—the result is a harmless, non-toxic pinch that rarely breaks the skin.
Globally, only two lizard species are known to be venomous: the Gila monster and the Mexican beaded lizard. Both are native to specific arid regions of North America and are not the small species found inside homes. The common house gecko poses no threat of toxic exposure and is often welcomed because it consumes household insects.
Understanding Actual Health Risks
While house lizards are not toxic, they can carry a bacterial risk. The primary health concern associated with all reptiles, including house geckos, is the potential transmission of Salmonella bacteria. This bacteria naturally lives in their intestinal tracts and is shed through their droppings.
Transmission occurs through the fecal-oral route, not through a bite or touch of the lizard itself. A person must ingest the bacteria, often by touching a contaminated surface and then touching their mouth or food. Salmonella can survive in gecko feces for several weeks, allowing the bacteria to contaminate surfaces in a home.
An infection with Salmonella, known as Salmonellosis, typically causes symptoms that resemble severe gastroenteritis. Common signs appear within 12 to 72 hours and include diarrhea, abdominal cramps, fever, and sometimes vomiting. Most healthy individuals recover within a week without treatment. However, infants, the elderly, and those with compromised immune systems are at a higher risk for severe illness, which may require medical intervention.
Practical Steps for Safe Coexistence
The low risk of bacterial infection is easily managed by establishing simple household hygiene protocols. The most effective way to prevent Salmonella transmission is to avoid direct contact with lizard droppings. Gecko feces, which are small, dark pellets with a white tip, should be cleaned up immediately using a paper towel and a disinfectant.
It is advised to wash hands thoroughly with soap and water immediately after any contact with a house lizard or any surface where one has been observed. To reduce the presence of geckos within the home, remove their food source by controlling the population of insects like cockroaches and moths. If removal is desired, it should be done humanely, such as guiding the animal into a container and releasing it outside, followed by cleaning the area to remove residual bacteria.