Almost all bath bomb recipes call for the same ingredients and measurements, with a few occasional exceptions. The key to great bath bombs is citric acid, which isn't hard to find online.
There are, of course, alternatives for those with sensitive skin. Citric acid, for instance, can be swapped for lemon juice, cream of tartar, buttermilk powder, or a mix of baking powder and apple cider vinegar. Food coloring could also cause a reaction—so if you're sensitive, just don't use any (or try a natural variety). Most of the other ingredients, including oils and cornstarch, are frequently used to treat sensitive skin (but avoid if you notice a negative reaction). If you have sensitive skin, or skin prone to eczema, it is best to avoid any products with fragrances. Additionally, although alpha hydroxy acids are great chemical exfoliators, they can also be irritating for sensitive skin.
If you'd rather not shop online and prefer the IRL approach, you may be able to purchase citric acid from your local pharmacy. Here's everything you'll need for the perfect bath bomb:
Step 1: With the exception of the citric acid, mix the dry ingredients in a large mixing bowl.
Step 2: Pour all of the liquid ingredients into a jar with a top. Close the jar and shake it vigorously.
Step 3: Pour the liquid mixture into the bowl of dry ingredients, and use your hands to combine and meld together. At this point, add the citric acid. You'll probably notice a slight fizzing reaction because of the citric acid. No need to panic, as this is normal.
Step 4: Mash the mixture into your chosen molds very tightly. You can overfill the molds slightly and use a spoon or glass to press the mixture in as tightly as possible. Immediately loosen the bombs from their molds onto wax paper and let them dry overnight.
Step 5: Give the bath bombs a day or two to completely dry before using them or wrapping them up as gifts.
Step 6: Pop one in the bathtub, enjoy the burst of colors and fizz and inhale the released aromas. Turn on some of your favorite music or a podcast to accompany you while you soak, or simply slide into the bath and enjoy all of your hard work.