diff --git a/README.md b/README.md
index 2489d88..b3a2cf3 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,11 @@ time: 240
 ```
 - `name` (string) - The displayed name of the recipe. Does not appear in the URL.
 - `author` (string, optional) - The author of the recipe.
-- `ingredients` (list) - Each entry in `ingredients` consists of an amount, ingredient name, and unit terminology. `[2, flour, cups]` is displayed as `2 cups of flour`, while `[1, egg, null]` is displayed as `1 egg`. The third field is optional - `[1, egg, null]` is the same as `[1, egg]`.
+- `ingredients` (list) - Each entry in `ingredients` is an array consisting of up to four items:
+	- amount (number) - The amount of this item to add, e.g. `2` for 2 cups of flour.
+	- ingredient name (string) - The name of the ingredient, e.g. `flour` for 2 cups of flour.
+	- unit terminology (string, optional) - The unit that amount refers to, e.g. `cups` for 2 cups of flour. If left blank or null, as in `[1, egg]`, the output will simply be "1 egg".
+	- optional (boolean, optional) - Whether or not this ingredient is optional. The ingredient `[1, chocolate egg, null, true]` produces "1 chocolate egg" and marks is as optional. Defaults to `false`.
 - `method` (list) - A list of steps undertaken to create the recipe, written in plain English. Or whatever language you prefer.
 - `time` (string, optional) - The time it takes to make the recipe in minutes.
 
diff --git a/_includes/ingredients.html b/_includes/ingredients.html
index 7eb25a0..ca305da 100644
--- a/_includes/ingredients.html
+++ b/_includes/ingredients.html
@@ -3,8 +3,8 @@
 	{%- assign tag = "h4" -%}
 {%- endif -%}
 <{{tag}}>Ingredients</{{tag}}>
-<ul>
+<ul class='ingredients'>
 	{% for item in page.ingredients -%}
-	<li>{{ item[0] }} {%- if item[2] %} {{ item[2] }} of {%- endif %} {{ item[1] }}</li>
+	<li class='{% if item[3] %}optional{% endif %}'>{{ item[0] }} {%- if item[2] %} {{ item[2] }} of {%- endif %} {{ item[1] }}</li>
 	{% endfor -%}
 </ul>
diff --git a/style.css b/style.css
index a669de0..9392b3b 100644
--- a/style.css
+++ b/style.css
@@ -35,6 +35,11 @@ h4 {
 	margin: 0.75em 0;
 }
 
+.ingredients li.optional::before {
+	content: "(Optional) ";
+	font-style: italic;
+}
+
 .subrecipe {
 	background: #eee;
 	padding: 10px;