An important fact to always keep in mind is that to the iguanas, it should manipulate them to him with caution, because if you those taking of the line, they loose it the same as the small lizards and, although later it grows them again, this will be shorter and you/they can be infected when it is recently cut. In this case, it is necessary to clean them the line rest with abundant water, oxygenated and alcohol yodado to disinfect. 
The iguanas constantly change the skin; the time that lapses among each change, will depend on the food, the estrés of the iguana, the terrario and another series of factors. It is not necessary to take out them the skin when this he/she is falling, but yes you can help him taking out him that is to say the small skin pieces that they have left in the face, the pieces that he has left around the eardrum, eyes, tablet sub-timpánica, nasal holes, jowl and mouth with much care of not hurting them. 
Some people accustom to take a bath to the iguanas, act that should have some cares: the water should be lukewarm and don't fry neither boiling; if the water has a high content of chlorine, it is better not to take a bath them or to add him before some minutes to the water some pills anticloro that are used for desclorar the water of the aquariums of fish. The iguanas in wild state swim in small streams and rivers, so this action doesn't affect them for anything. Some iguanas also like to defecate inside the water. 
The green iguanas (Iguana iguana) they live in wild state in the tropical forests from the north of Mexico until Peru and the south of Brazil, in countries and islands that present a humidity and high temperature. The iguanas live in the mountains, on the trees to a height of about 15 or 30 meters, reaching the solar rays that need to maintain their internal heat, since they are ectopoiquilotermas, that is to say, the heat for its internal metabolism receives it from the means and they don't produce it. The day they pass climbing the branches and taking sun in near sectors to the water. Their brilliant green color helps them to be protected against depredadores among the vegetables which he/she eats: leaves, flowers and fruits. The oldest iguanas live higher in the trees where there is more light and it is drier, on the other hand the young iguanas live more near the floor, since they require of an atmosphere with a bigger humidity. 
The iguanas are not in extinction state in any part of the world. Also, most of the mascoterías (for not saying all) he/she sells born iguanas and maids in hatcheries for this end and they are not taken out of the humid forests. In Central America it is very common to find these farms of iguanas that raise them for sales like mascots and to also eat them. 
The care that the iguanas require, is bigger than the one that a salesperson of mascots will tell you, but not much bigger. You should also consider that with the iguanas he/she wears out a lot of money, in terrarios, visits to the veterinary doctor, heating, etc. and a lot of time, in preparing the food, taming the iguana, taking out it in the sun, etc.  
In the event of illness, it is not advisable to trust alone in a salesperson of mascots. Them (generally), they only need to maintain the alive animals the enough time to sell them. In these cases, or before any problem with the iguanas, it is necessary to take them immediately to a veterinarian, (as much as possible, specialized in reptiles).