diff --git a/functions/validate_values.py b/functions/validate_values.py
index 2159269..53469f6 100644
--- a/functions/validate_values.py
+++ b/functions/validate_values.py
@@ -13,12 +13,18 @@ def create_dynamic_schema() -> Type[Schema]:
 
     for attrib in item_attributes:
         if isinstance(attrib, textAttribute):
+            # Allowed chars
+            def validate_allowed_chars(value: str, attrib=attrib) -> None:
+                if attrib.allowed_chars and not all(char in attrib.allowed_chars for char in value):
+                    raise ValidationError(f"Invalid characters in {attrib.display_name}. Allowed characters are: {attrib.allowed_chars}")
+                    
             schema_fields[attrib.attrib_name] = fields.String(
                 required=attrib.required,
                 validate=[
                     lambda x, attrib=attrib: len(x) <= attrib.max_length if attrib.max_length else True,
                     lambda x, attrib=attrib: len(x) >= attrib.min_length if attrib.min_length else True,
                     lambda x, attrib=attrib: re.match(attrib.regex, x) if attrib.regex else True,
+                    validate_allowed_chars,
                 ],
                 error_messages={
                     "required": f"{attrib.display_name} is required.",