You consider the following possibilities to find the information you need to answer his question:
What if the line is busy? Or how current and accurate is your colleague's information? Would a librarian point you in the right direction?
This is time-consuming and limited. Maybe the article you saw was written a year or two ago and you no longer have the article. There are more effective ways of finding current journal articles or primary sources of information.
Finding the information in one place in one quick look-up is the most time efficient method. However, be sure to check the date of the book and the credentials of the author and source. You may still need to turn to other sources. Books and full-text databases are also called tertiary sources.
Using bibliographic databases or search engines (also known as secondary sources) is an effective means of locating current information on topics. It takes longer than finding information in a tertiary source however.
What is a reasonable path to follow in finding information about medications?
Here is a suggested path to finding an answer for both his question and your questions.
You'd prefer to find summarized information [categorizing information needed] rather than original research, therefore you begin with tertiary resources [selecting resource type].
Because tea tree oil is an herbal supplement, you choose Natural Standard as your entry point [selecting a specific resource]. Reviewing the information available, you select Bottom Line and read that tea tree oil has limited evidence.
Alternatively, you choose Natural Medicines Comprehensive Database as your entry point [selecting a specific resource]. Reviewing the information available, you select Effectiveness and read that it varies depending upon the strength used.
You may choose to print off the information for him and you can follow up on the references listed as well as search PubMed for additional materials.