diff --git a/packages/app-insights/src/react/utils.ts b/packages/app-insights/src/react/utils.ts
index 97a36bf92..636664f4b 100644
--- a/packages/app-insights/src/react/utils.ts
+++ b/packages/app-insights/src/react/utils.ts
@@ -1 +1,5 @@
+/**
+ * **CAUTION:** This function takes the last two parts of the hostname which may cause issues for
+ * some second-level domains, e.g. `.co.uk`.
+ */
 export const getPrimaryDomain = () => window.location.hostname.split('.').slice(-2).join('.');