Creams, gels and sprays can apply a treatment directly to an area of wounded skin and are called topical or local treatments. They don’t really pass into our bloodstream so don’t affect any other parts of the body. 

Topical treatments are made up of an inactive substance called the ‘base’ and an ‘active ingredient’ that has biological effects on the body. The base might be a greasy cream, a blobby gel or watery liquid for dropping or spraying and a small amount of an active ingredient may be mixed into the base. Some creams are beneficial on their own by providing a protective barrier or helping to keep skin flexible while it heals but a medicated cream contains an active ingredient at a specific dose and may need to be used a certain number of times per day to be effective and not more than this. Researchers need to find out how much of their active ingredient to mix in with the base, what sort of base to use, how runny or sticky it needs to be, whether it needs to be shaken before use to mix the active ingredient evenly through it or stored in the fridge or freezer to keep the active ingredient working. They may look at ways to reduce stinging or take away an unpleasant taste or smell.

Some researchers study the methods of drug delivery rather than the actual drugs themselves. To make the best medicines, the two groups of experts can work together.