Can tresaderm be used on humans?

Actually Merck makes Tresaderm for humans under a different name. It is MINTEZOL (Thiabendazole) is an anthelmintic provided as 500 mg chewable tablets, and as a suspension, containing 500 mg thiabendazole per 5 mL

The only difference is it is in a chewable tablet. Whether you chew it or apply drops on your skin, it will be absorbed into your blood stream. (how it got in is not the critical part) the question would be can a human ingest or take Thiabendazole (Tresaderm/Mintezol) and the answer is yes. Naturally please call the doc or vet :) before you put the drops on your skin or in your ear.

No - it is for animal use only. Its safety in humans has not been established.