diff --git a/README.md b/README.md
index 44264f6c13..7ec0dd0836 100755
--- a/README.md
+++ b/README.md
@@ -510,7 +510,11 @@ You can specify config defaults that will be applied to every request.
 
 ```js
 axios.defaults.baseURL = 'https://api.example.com';
+
+// Important: If axios is used with multiple domains, the AUTH_TOKEN will be sent to all of them.
+// See below for an example using Custom instance defaults instead.
 axios.defaults.headers.common['Authorization'] = AUTH_TOKEN;
+
 axios.defaults.headers.post['Content-Type'] = 'application/x-www-form-urlencoded';
 ```