Both are applied to the skin, so people often use the words interchangeably. Clinically, the intent differs.
Topical
The goal is a local effect on the skin or the tissue just beneath it, such as treating a rash. Ideally little of the drug reaches the bloodstream.
Transdermal
The goal is for the drug to cross the skin and act elsewhere in the body. How much is absorbed depends on the drug, the base, the skin site and the individual. Many drugs do not cross skin well enough to work this way.
Practical points
- Apply exactly where and how the label directs.
- Wash hands after applying unless the hands are the treatment site.
- Keep treated skin away from children and pets where the label says to.
- Report skin irritation to the pharmacist or prescriber.
This article is educational and is not medical or veterinary advice. Talk with your prescriber, veterinarian or pharmacist about your own situation.