Teach Soap

What the title says. I'm very confused about this xD

The bath bombs are just a basic recipe of 2 parts baking soda to 1 part citric acid. Also micas and fragrances (used energy in one batch and sore muscle in another. Both from Brambleberry.)
The bath salts are 4 cups dead sea salts, 4 cups epsom salts, 1 1/2 cups baking soda, and 1 ounce of sore muscle blend mixed with 3/4 cup dendritic salt. Mica in this as well.

Now, I know plastic isn't a good long term storage option, but it's what I'm using to transport the stuff to my parents place (they're gifts for my dad. He loooves his baths.) But imagine my shock when I look over to where they're sitting about an hour later to see the bags poofed up to capacity! What's going on here?

Dead sea salts attract moisture from the air. Baking soda & citric acid (a bath bomb) react to moisture by fizzing like crazy. So, carbon dioxide is formed and has no where to go, thus expanding the bags.

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Genny

It's a good job you didn't put them in glass bottles or you might have been writing from hospital!
If you're making things that fizz, use anyhydrous ingredients only, and package them in hermetically sealed containers that won't pose a risk to health if there is a CO2 build-up.