Edible Glow-in-the-Dark Marshmallow Slime

This spooky glow-in-the-dark slime recipe is perfect for Halloween! It only a takes a few minutes to make, and because it’s made using only edible ingredients, it’s perfectly safe for little ones who like to put things in their mouths! Your kids will love playing with this cool DIY marshmallow slime that glows under black light!

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Before I had kids and tried making slime at home, I never understood why everyone was so obsessed with it. But I have to admit that ever since we started making it, I’ve been hooked!

We do often make slime using contact lens solution for our four-year-old. It’s so quick and easy, and she loves playing with it while her younger siblings are napping!

But since we have two toddlers at home, we also like to come up with recipes that are edible, or at the very least taste-safe. Our one-year-old and our three-year-old love to be included in the fun, and it reassures me to know that they’ll be safe even if they decide to have a little nibble!

Note: If you’re in the same boat, you might also want to check out our recipe for Taste-Safe Psyllium Husk Slime. It’s super simple to make, and it’s definitely our go-to recipe for taste-safe slime!

About this Recipe

This recipe is doubly cool because it’s both edible and glow-in-the-dark!

Yes, you read that correctly. Did you know that it’s possible to make food that glows under black light?

The secret ingredient that makes this possible is tonic water. Tonic water contains an ingredient called “quinine” which glows when exposed to black light. So be sure to double-check the ingredients of the brand that you buy so you don’t end up disappointed!

Quinine Makes Tonic Water Glow Under Black Light

How to Make Edible Glow-in-the-Dark Marshmallow Slime

Required Ingredients

Here’s what you’ll need to make your very own edible slime that glows under black light:

If you want to see your slime glow, you’ll also need a black light. But if you don’t happen to have one on hand, this edible slime is still lots of fun to play with!

Important: The brand of tonic water you buy must list “quinine” as an ingredient, since this is what causes it to glow.

Step-by-Step Instructions

1. Melt Marshmallows

Start by melting 10 marshmallows by placing them in a microwave-safe bowl and cooking them for about 30 seconds on high.

Once you take them out, you’ll know they’re ready if you can stir them with a spoon without leaving any clumps. If not, put them back in the microwave for a few seconds until they’re fully melted.

2. Add Tonic Water

Add ¼ cup of tonic water to the melted marshmallows and stir the mixture with a spoon until the ingredients are well combined.

3. Add Cornstarch

Add 10 tablespoons of cornstarch, a few tablespoons at a time, and keep stirring until all the ingredients are well combined.

4. Adjust Texture

We thought the texture of our slime was perfect with the proportions listed in this recipe, but you might want to adjust the quantities to suit your personal preferences.

If you like slime that’s runny and behaves like goop, simply add more tonic water. If you prefer slime with a more putty-like consistency, add cornstarch. I recommend adding only a little bit at a time so you can stop as soon as you reach the desired consistency!

Playing with Glowing Marshmallow Slime

Once you’ve adjusted the quantities, the slime is ready to play with!

It has an awesome texture, but it can get a little messy. So be sure that the surface your child is playing on is well protected—or at the very least, easy to clean!

It’s really fun to play with even under regular lighting, but if you’d like to see it glow, simply turn off the lights and shine a black light on it!

Note: The glow from our slime was a little dim because we chose to use lots of marshmallows to improve its texture and flavour. But if having a strong glow is important to you, you can always reduce the quantity of marshmallows or increase the quantity of tonic water and cornstarch!

I hope your kids have as much fun playing with this slime as ours did!

Edible Glow-in-the-Dark Marshmallow Slime

The Craft-at-Home Family
This spooky glow-in-the-dark slime recipe is perfect for Halloween—and it also happens to be made from edible ingredients!
No ratings yet
Prep Time 5 minutes


  • 10 marshmallows
  • ¼ cup tonic water
  • 10 tbsp cornstarch


  • Melt marshmallows by placing them in a microwave-safe bowl and cooking them for about 30 seconds on high.
  • Use a spoon to stir the marshmallows. Add the tonic water and stir until well combined.
  • Stir in the cornstarch one tablespoon at a time. Keep stirring until the mixture feels totally smooth.
  • Adjust the consistency of the slime as needed by adding more tonic water or more cornstarch. Then, give the slime to your child and let them play!
Keyword cornstarch, edible slime, glow-in-the-dark, halloween, marshmallows, slime, tonic water
Tried this recipe?Let us know how it was!

Related Glow-in-the-Dark Activities

Looking for more fun glow-in-the-dark activities that are safe for littles ones to taste? Check out this article:

And if your kids love glowing sensory activities, they might also enjoy these easy crafts made using glow-in-the-dark stars:

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The Craft-at-Home Family