All database search systems allow for wildcards and truncation.
These symbols allow you to search on:

• both the singular and plural forms of a word
• words that begin with the same word stem
• words that can be spelled in different ways

This is especially important to your search strategy as most of the databases you have access to are American and use American spelling.
Allowing for word variations will return a larger result, as well as increase your search efficiency.

• Example: use truncation to find word variations
  allerg* to find allergies, allergic, allergens

• Example: wildcards to find alternate spelling
  p?ediatric to find paediatric, pediatric

• Example: truncation to find plurals
  infant* to find infant, infants

Note: Truncation and wildcard symbols vary between databases. Check the online Help to find which symbols apply to the database you are using.