Veiled Cham Guy
A vet check will likely diagnose this with certainty, but it sounds like an upper esophageal infection, which is not all that different from a respiratory infection in some ways. Upper E. infections are due to an excessive build-up of bacteria in the mouth and upper esophagus. It is not caused by temperature/humidity issues as most repiratory infections may be. It is usually due to the introduction of large quantities of otherwise common bacteria into the chameleons mouth via its food, most commonly scavenger bugs like crickets.
Lets assume crickets. What happens is that the cricket is ingesting from a bacterial stew somewhere, which means accesss to moisture and crud. This may be wherever you house your crickets, or possibly, right in the chameleon's cage. If in your cricket bin, any water source that is not removed and disinfected every two days or less becomes a source. If not done at least every four days its a guarantee. This includes those cricket water pellets/bites, sponge-bottom waterers, etc. If using the water pellets (or whatever they are called, I avoid them like the plague), fully take out and wipe clean any corner/dish they are in, and use a different corner/clean dish every two days. In your chameleon's cage, many people have live plants with a plastic dish beneath it to catch/hold water runoff from the plant. Standing water there will be contaminated easily, then consumed by crickets, who can handle high bacteria consumption. All of the above turn crickets into what we call "poison pills".
Symptoms are as you describe. Visual build-up of gummy mucous, but no labored breathing (at first). As it worsens, this mucous will dry outside the lip, forming an ugly crust at times. It will likely not go away on its own, and will eventually overwhelm and kill the animal. This can usually take a month or more. It is also easily diagnosed and confirmed via a culture and sensitivity panel (about $75 at your vet's), and responds to common orally administerd antibiotics. You must find and eliminate the source as well.
It is our experience that this type of infection is more common in the hobby than URI's (Upper Respiratory Infections). It is often semi-diagnosed as such, and with a culture, is then remedied in the animal as if it were a URI, which will work. Problem is, the bacteria source / causitive husbandry deficiency goes unremedied, and it can happen all over again. Hope this helps.
