The only two lizards known to be poisonous are the
Beaded lizard
Gila monster
The beaded lizard is present in Mexico. The Gila monster is present in Arizona, Sonora, Mexico, and adjacent areas.
The venom of these lizards is somewhat similar in content and effect to that of some pit vipers Pit vipers Venomous snakes in the United States include pit vipers (rattlesnakes, copperheads, and cottonmouths) and coral snakes. Severe envenomation can cause damage to the bitten extremity, bleeding... read more 
, although symptoms tend to be much less severe, and bites are almost never fatal. Unlike most snakes, the Gila monster and beaded lizard clamp on firmly when they bite and chew the venom into the person rather than injecting it through fangs. The lizard may be difficult to dislodge.
Common symptoms include pain, swelling, and discoloration in the area around the bite as well as swollen lymph nodes. Weakness, sweating, thirst, headache, and ringing in the ears (tinnitus) may develop. In severe cases, blood pressure may fall.
Various suggestions for removing Gila monsters include the following:
Forcing the jaws open with pliers
Applying a flame under the lizard’s chin
Immersing the lizard and body extremity under water
Once the lizard has been detached, tooth fragments often remain in the skin and must be removed. Treatment of low blood pressure or blood clotting problems is similar to that of pit viper bites Treatment Venomous snakes in the United States include pit vipers (rattlesnakes, copperheads, and cottonmouths) and coral snakes. Severe envenomation can cause damage to the bitten extremity, bleeding... read more . A specific antivenom is not available.
(See also Introduction to Bites and Stings Introduction to Bites and Stings Many creatures, including humans, bite when frightened or provoked. Others include Alligators and crocodiles Iguanas Mites Ticks read more .)
