Handling
Having read through a number of different "handling" threads, and as someone new to the forum, but not new to chameleons, I can see how someone new to chameleons could be confused by the information and pictures present. My observations about the approaches that experienced keepers on this forum adopt concerning the handling issue:
1) Chameleons, as a group, are solitary, slowish moving (but very vigilant) animals that depend mostly upon crypsis to avoid predation. In almost every category, they are the exact opposite of "pets" we are most used to such as dogs and hamsters. They are wired to avoid being seen, much less handled.
2) It is o.k. to occasionally handle an animal that has been slowly and patiently conditioned to being handled. This conditioning process can take weeks to months depending on the chameleon's "personality", species, whether it was wc or cb, its age, etc. A patiently conditioned chameleon will experience little or no stress when allowed to interact with its keeper on its own terms. (I have experienced this). The pictures of experienced handlers holding their animals are, for the most part, the result of a long succession of positive interactions and trust building that did not occur overnight.
3) The process of conditioning requires patience and time and cannot be pushed upon the animal.
4) Different animals and different species adjust at different rates. (Some never do)
5) New animals from pet stores (buy from reptile specific pet shops, reputable breeders or conscientious importers instead!!!!!!!!) should not be handled or stressed for several weeks or months after purchase as they have plenty of stress response hormone in their systems and need time to settle into a new and healthy flow. They will not thrive until they feel safe and comfortable in their new place. And they will not respond positively to conditioning until they feel secure.
6) I would add that human hands are notoriously filthy vectors. We do not yet well understand how pathogens affect different species differently. For the most part, it seems pathogens are fairly species specific, but all bets are off when we are talking about stressed organisms and inappropriate husbandry. To complicate any individual experiences, reptiles tend to respond more slowly to problems in their environment than, say mammals, so cause and affect are not always obvious. Sanitizing hands prior to working with enclosure materials, food items and your chameleon is probably not a bad idea. This will not guarantee that your animal won't get, say, a respiratory infection. But it will greatly reduce your animals exposure to bacteria and viruses that are uncommon in their native habitat. Er on the side of cleanliness.
I am receiving a wonderful, continuing education on this forum and it is thanks to all the experienced keepers that have so much information to share because they love and understand these animals.