diff --git a/check_docker/check_docker.py b/check_docker/check_docker.py
index 73fb2d0..33d7619 100755
--- a/check_docker/check_docker.py
+++ b/check_docker/check_docker.py
@@ -952,17 +952,25 @@ def socketfile_permissions_failure(parsed_args):
         return False
 
 
+def sort_by_severity(messages):
+    severities = ('CRITICAL: ', 'WARNING: ', 'UNKNOWN: ', 'OK: ')
+    rank = lambda message: next((index for index, severity in enumerate(severities)
+                                 if message.startswith(severity)), len(severities))
+    return sorted(messages, key=rank)
+
+
 def print_results():
+    # Nagios notifications only carry the first line of the plugin output
     if no_ok:
         # Remove all the "OK"s
         filtered_messages = [message for message in messages if not message.startswith('OK: ')]
         if len(filtered_messages) == 0:
             messages_concat = 'OK'
         else:
-            messages_concat = '\n'.join(filtered_messages)
+            messages_concat = ', '.join(sort_by_severity(filtered_messages))
 
     else:
-        messages_concat = '\n'.join(messages)
+        messages_concat = ', '.join(sort_by_severity(messages))
 
     if no_performance or len(performance_data) == 0:
         print(messages_concat)
diff --git a/check_docker/check_swarm.py b/check_docker/check_swarm.py
index 6b75987..6de5619 100755
--- a/check_docker/check_swarm.py
+++ b/check_docker/check_swarm.py
@@ -360,8 +360,16 @@ def socketfile_permissions_failure(parsed_args):
     return False
 
 
+def sort_by_severity(messages):
+    severities = ('CRITICAL: ', 'WARNING: ', 'UNKNOWN: ', 'OK: ')
+    rank = lambda message: next((index for index, severity in enumerate(severities)
+                                 if message.startswith(severity)), len(severities))
+    return sorted(messages, key=rank)
+
+
 def print_results():
-    print('\n'.join(messages))
+    # Nagios notifications only carry the first line of the plugin output
+    print(', '.join(sort_by_severity(messages)))
 
 
 def perform_checks(raw_args):
diff --git a/tests/test_check_docker.py b/tests/test_check_docker.py
index 2eea30a..4803dd7 100644
--- a/tests/test_check_docker.py
+++ b/tests/test_check_docker.py
@@ -709,8 +709,11 @@ def test_perform(check_docker, fs, args, called):
 
 @pytest.mark.parametrize("messages, perf_data, expected", (
         (['TEST'], [], 'TEST'),
-        (['FOO', 'BAR'], [], 'FOO\nBAR'),
-        (['FOO', 'BAR'], ['1;2;3;4;'], 'FOO\nBAR|1;2;3;4;')
+        (['FOO', 'BAR'], [], 'FOO, BAR'),
+        (['FOO', 'BAR'], ['1;2;3;4;'], 'FOO, BAR|1;2;3;4;'),
+        (['OK: FOO', 'WARNING: BAR', 'CRITICAL: BAZ', 'UNKNOWN: QUX'], [],
+         'CRITICAL: BAZ, WARNING: BAR, UNKNOWN: QUX, OK: FOO'),
+        (['WARNING: FOO', 'WARNING: BAR'], [], 'WARNING: FOO, WARNING: BAR')
 ))
 def test_print_results(check_docker, capsys, messages, perf_data, expected):
     # These sometimes get set to true when using random-order plugin, for example --random-order-seed=620808
@@ -726,12 +729,13 @@ def test_print_results(check_docker, capsys, messages, perf_data, expected):
 @pytest.mark.parametrize("messages, perf_data, no_ok, no_performance, expected", (
         ([], [], False, False, ''),
         (['TEST'], [], False, False, 'TEST'),
-        (['FOO', 'BAR'], [], False, False, 'FOO\nBAR'),
-        (['FOO', 'BAR'], ['1;2;3;4;'], False, False, 'FOO\nBAR|1;2;3;4;'),
+        (['FOO', 'BAR'], [], False, False, 'FOO, BAR'),
+        (['FOO', 'BAR'], ['1;2;3;4;'], False, False, 'FOO, BAR|1;2;3;4;'),
         ([], [], True, False, 'OK'),
         (['OK: TEST'], [], True, False, 'OK'),
         (['OK: FOO', 'OK: BAR'], [], True, False, 'OK'),
         (['OK: FOO', 'BAR'], ['1;2;3;4;'], True, False, 'BAR|1;2;3;4;'),
+        (['OK: FOO', 'WARNING: BAR', 'CRITICAL: BAZ'], [], True, False, 'CRITICAL: BAZ, WARNING: BAR'),
         ([], [], False, True, ''),
         (['OK: TEST'], [], False, True, 'OK: TEST'),
         (['OK: TEST'], ['1;2;3;4;'], False, True, 'OK: TEST'),
diff --git a/tests/test_check_swarm.py b/tests/test_check_swarm.py
index 4df8d22..37e3685 100644
--- a/tests/test_check_swarm.py
+++ b/tests/test_check_swarm.py
@@ -391,7 +391,9 @@ def test_check_not_swarm_service(check_swarm, fs):
 @pytest.mark.parametrize("messages, perf_data, expected", (
         ([], [], ''),
         (['TEST'], [], 'TEST'),
-        (['FOO', 'BAR'], [], 'FOO\nBAR'),
+        (['FOO', 'BAR'], [], 'FOO, BAR'),
+        (['OK: FOO', 'WARNING: BAR', 'CRITICAL: BAZ', 'UNKNOWN: QUX'], [],
+         'CRITICAL: BAZ, WARNING: BAR, UNKNOWN: QUX, OK: FOO'),
 ))
 def test_print_results(check_swarm, capsys, messages, perf_data, expected):
     check_swarm.messages = messages