diff --git a/core.go b/core.go
index 4b36dd4..c5eb51f 100644
--- a/core.go
+++ b/core.go
@@ -15,7 +15,7 @@ type core struct {
 	// permLabels is a collection of labels that have been added to the logger
 	// through the use of `With()`. These labels should never be cleared after
 	// logging a single entry, unlike `tempLabel`.
-	permLabels labels
+	permLabels *labels
 
 	// tempLabels keeps a record of all the labels that need to be applied to the
 	// current log entry. Zap serializes log fields at different parts of the
@@ -26,27 +26,29 @@ type core struct {
 	// Instead, we have to filter out these labels at both locations, and then add
 	// them back in the proper format right before we call `Write` on the original
 	// Zap core.
-	tempLabels labels
+	tempLabels *labels
 }
 
 // WrapCore returns a `zap.Option` that wraps the default core with the
 // zapdriver one.
 func WrapCore() zap.Option {
 	return zap.WrapCore(func(c zapcore.Core) zapcore.Core {
-		return &core{c, labels{}, labels{}}
+		return &core{c, newLabels(), newLabels()}
 	})
 }
 
 // With adds structured context to the Core.
 func (c *core) With(fields []zap.Field) zapcore.Core {
-	var lbls labels
+	var lbls *labels
 	lbls, fields = c.extractLabels(fields)
 
-	for k, v := range lbls {
-		c.permLabels[k] = v
+	lbls.mutex.Lock()
+	for k, v := range lbls.store {
+		c.permLabels.store[k] = v
 	}
+	lbls.mutex.Unlock()
 
-	return &core{c.Core.With(fields), c.permLabels, labels{}}
+	return &core{c.Core.With(fields), c.permLabels, newLabels()}
 }
 
 // Check determines whether the supplied Entry should be logged (using the
@@ -64,17 +66,19 @@ func (c *core) Check(ent zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.Check
 }
 
 func (c *core) Write(ent zapcore.Entry, fields []zapcore.Field) error {
-	var lbls labels
+	var lbls *labels
 	lbls, fields = c.extractLabels(fields)
 
-	for k, v := range lbls {
-		c.tempLabels[k] = v
+	lbls.mutex.Lock()
+	for k, v := range lbls.store {
+		c.tempLabels.store[k] = v
 	}
+	lbls.mutex.Unlock()
 
 	fields = append(fields, labelsField(c.allLabels()))
 	fields = c.withSourceLocation(ent, fields)
 
-	c.tempLabels = labels{}
+	c.tempLabels = newLabels()
 
 	return c.Core.Write(ent, fields)
 }
@@ -84,47 +88,54 @@ func (c *core) Sync() error {
 	return c.Core.Sync()
 }
 
-func (c *core) allLabels() labels {
-	lbls := labels{}
-	for k, v := range c.permLabels {
-		lbls[k] = v
+func (c *core) allLabels() *labels {
+	lbls := newLabels()
+
+	lbls.mutex.Lock()
+	for k, v := range c.permLabels.store {
+		lbls.store[k] = v
 	}
 
-	for k, v := range c.tempLabels {
-		lbls[k] = v
+	for k, v := range c.tempLabels.store {
+		lbls.store[k] = v
 	}
+	lbls.mutex.Unlock()
 
 	return lbls
 }
 
-func (c *core) extractLabels(fields []zapcore.Field) (labels, []zapcore.Field) {
-	lbls := labels{}
+func (c *core) extractLabels(fields []zapcore.Field) (*labels, []zapcore.Field) {
+	lbls := newLabels()
 	out := []zapcore.Field{}
 
+	lbls.mutex.Lock()
 	for i := range fields {
 		if !isLabelField(fields[i]) {
 			out = append(out, fields[i])
 			continue
 		}
 
-		lbls[strings.Replace(fields[i].Key, "labels.", "", 1)] = fields[i].String
+		lbls.store[strings.Replace(fields[i].Key, "labels.", "", 1)] = fields[i].String
 	}
+	lbls.mutex.Unlock()
 
 	return lbls, out
 }
 
 func (c *core) withLabels(fields []zapcore.Field) []zapcore.Field {
-	lbls := labels{}
+	lbls := newLabels()
 	out := []zapcore.Field{}
 
+	lbls.mutex.Lock()
 	for i := range fields {
 		if isLabelField(fields[i]) {
-			lbls[strings.Replace(fields[i].Key, "labels.", "", 1)] = fields[i].String
+			lbls.store[strings.Replace(fields[i].Key, "labels.", "", 1)] = fields[i].String
 			continue
 		}
 
 		out = append(out, fields[i])
 	}
+	lbls.mutex.Unlock()
 
 	return append(out, labelsField(lbls))
 }
diff --git a/core_test.go b/core_test.go
index 4cad94c..cef1233 100644
--- a/core_test.go
+++ b/core_test.go
@@ -19,17 +19,20 @@ func TestWithLabels(t *testing.T) {
 		Label("two", "value"),
 	}
 
+	labels := newLabels()
+	labels.store = map[string]string{"one": "value", "two": "value"}
+
 	want := []zap.Field{
 		zap.String("hello", "world"),
-		zap.Object("labels", labels(map[string]string{"one": "value", "two": "value"})),
+		zap.Object("labels", labels),
 	}
 
 	assert.Equal(t, want, (&core{}).withLabels(fields))
 }
 
 func TestExtractLabels(t *testing.T) {
-	var lbls labels
-	c := &core{zapcore.NewNopCore(), labels{}, labels{}}
+	var lbls *labels
+	c := &core{zapcore.NewNopCore(), newLabels(), newLabels()}
 
 	fields := []zap.Field{
 		zap.String("hello", "world"),
@@ -39,9 +42,12 @@ func TestExtractLabels(t *testing.T) {
 
 	lbls, fields = c.extractLabels(fields)
 
-	require.Len(t, lbls, 2)
-	assert.Equal(t, "world", lbls["one"])
-	assert.Equal(t, "worlds", lbls["two"])
+	require.Len(t, lbls.store, 2)
+
+	lbls.mutex.RLock()
+	assert.Equal(t, "world", lbls.store["one"])
+	assert.Equal(t, "worlds", lbls.store["two"])
+	lbls.mutex.RUnlock()
 
 	require.Len(t, fields, 1)
 	assert.Equal(t, zap.String("hello", "world"), fields[0])
@@ -86,8 +92,11 @@ func TestWithSourceLocation_OnlyWhenDefined(t *testing.T) {
 }
 
 func TestWrite(t *testing.T) {
+	temp := newLabels()
+	temp.store = map[string]string{"one": "1", "two": "2"}
+
 	debugcore, logs := observer.New(zapcore.DebugLevel)
-	core := &core{debugcore, labels{}, labels{}}
+	core := &core{debugcore, newLabels(), temp}
 
 	fields := []zap.Field{
 		zap.String("hello", "world"),
@@ -103,7 +112,7 @@ func TestWrite(t *testing.T) {
 
 func TestWithAndWrite(t *testing.T) {
 	debugcore, logs := observer.New(zapcore.DebugLevel)
-	core := zapcore.Core(&core{debugcore, labels{}, labels{}})
+	core := zapcore.Core(&core{debugcore, newLabels(), newLabels()})
 
 	core = core.With([]zapcore.Field{Label("one", "world")})
 	err := core.Write(zapcore.Entry{}, []zapcore.Field{Label("two", "worlds")})
@@ -117,7 +126,7 @@ func TestWithAndWrite(t *testing.T) {
 
 func TestWithAndWrite_MultipleEntries(t *testing.T) {
 	debugcore, logs := observer.New(zapcore.DebugLevel)
-	core := zapcore.Core(&core{debugcore, labels{}, labels{}})
+	core := zapcore.Core(&core{debugcore, newLabels(), newLabels()})
 
 	core = core.With([]zapcore.Field{Label("one", "world")})
 	err := core.Write(zapcore.Entry{}, []zapcore.Field{Label("two", "worlds")})
@@ -138,3 +147,22 @@ func TestWithAndWrite_MultipleEntries(t *testing.T) {
 	assert.Equal(t, "world", labels["one"])
 	assert.Equal(t, "worlds", labels["three"])
 }
+
+func TestAllLabels(t *testing.T) {
+	perm := newLabels()
+	perm.store = map[string]string{"one": "1", "two": "2", "three": "3"}
+
+	temp := newLabels()
+	temp.store = map[string]string{"one": "ONE", "three": "THREE"}
+
+	core := &core{zapcore.NewNopCore(), perm, temp}
+
+	out := core.allLabels()
+	require.Len(t, out.store, 3)
+
+	out.mutex.RLock()
+	assert.Equal(t, out.store["one"], "ONE")
+	assert.Equal(t, out.store["two"], "2")
+	assert.Equal(t, out.store["three"], "THREE")
+	out.mutex.RUnlock()
+}
diff --git a/label.go b/label.go
index 37899d6..0a2d149 100644
--- a/label.go
+++ b/label.go
@@ -2,6 +2,7 @@ package zapdriver
 
 import (
 	"strings"
+	"sync"
 
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
@@ -21,13 +22,15 @@ func Label(key, value string) zap.Field {
 // string `labels.` and their value type set to StringType. It then wraps those
 // key/value pairs in a top-level `labels` namespace.
 func Labels(fields ...zap.Field) zap.Field {
-	lbls := labels{}
+	lbls := newLabels()
 
+	lbls.mutex.Lock()
 	for i := range fields {
 		if isLabelField(fields[i]) {
-			lbls[strings.Replace(fields[i].Key, "labels.", "", 1)] = fields[i].String
+			lbls.store[strings.Replace(fields[i].Key, "labels.", "", 1)] = fields[i].String
 		}
 	}
+	lbls.mutex.Unlock()
 
 	return labelsField(lbls)
 }
@@ -36,16 +39,31 @@ func isLabelField(field zap.Field) bool {
 	return strings.HasPrefix(field.Key, "labels.") && field.Type == zapcore.StringType
 }
 
-func labelsField(l map[string]string) zap.Field {
-	return zap.Object("labels", labels(l))
+func labelsField(l *labels) zap.Field {
+	return zap.Object("labels", l)
 }
 
-type labels map[string]string
+type labels struct {
+	store map[string]string
+	mutex *sync.RWMutex
+}
+
+func newLabels() *labels {
+	return &labels{store: map[string]string{}, mutex: &sync.RWMutex{}}
+}
+
+func (l *labels) Add(key, value string) {
+	l.mutex.Lock()
+	l.store[key] = value
+	l.mutex.Unlock()
+}
 
 func (l labels) MarshalLogObject(enc zapcore.ObjectEncoder) error {
-	for k, v := range l {
+	l.mutex.RLock()
+	for k, v := range l.store {
 		enc.AddString(k, v)
 	}
+	l.mutex.RUnlock()
 
 	return nil
 }
diff --git a/label_test.go b/label_test.go
index 8cd1773..b2b5f10 100644
--- a/label_test.go
+++ b/label_test.go
@@ -23,5 +23,8 @@ func TestLabels(t *testing.T) {
 		Label("hi", "universe"),
 	)
 
-	assert.Equal(t, zap.Object("labels", labels{"hello": "world", "hi": "universe"}), field)
+	labels := newLabels()
+	labels.store = map[string]string{"hello": "world", "hi": "universe"}
+
+	assert.Equal(t, zap.Object("labels", labels), field)
 }