Bath Bombs Dismantled

Ever wondered what makes bath bombs foam, fizz and bubble? Curious about the benefits of a well made bath bomb (besides adding novelty to bath time)? Read on to find out.


Nearly all bath bombs contain baking soda and citric acid as the active ingredients, with some type of oil as a binder. Additional ingredients add additional features and benefits. When the bath water hits the baking soda and citric acid, a reaction is triggered, just like with your childhood vinegar and baking soda volcano. 

Below I've listed the properties and benefits of the Vesta bath bomb ingredients.

Baking Soda (sodium bicarbonate): Widely used chemical compound. It is basic (not in a PSL + Ugg boots sense), and when mixed with an acid, it releases carbon dioxide and gives baked goods levity and texture. Along with citric acid, baking soda is a key ingredient in bath bombs. The bath water activates the baking soda + acid reaction, which produces the characteristic bath bomb fizziness.

According to Medical News Today adding baking soda to the bath can be beneficial for many health conditions, including yeast infections, fungal skin and nail infections, eczema, psoriasis, poison ivy, poison oak, or sumac rashes, urinary tract infections, diaper rash, chickenpox,  vulva irritation, constipation, and hemorrhoids.
(Internationally, baking soda is also know as bicarbonate of soda, bread soda, cooking soda)

Basic Bitch Sticker by bellabello Redbubble
Image credit: bellabello

Citric acid is a weak organic acid that occurs naturally in citrus fruits and gives them their sour taste. Not to be confused with ascorbic acid (vitamin C).  It is part of a category of acids called AHAs (alpha hydroxy acids) that help smooth and exfoliate skin. Along with baking soda, citric acid is one of the two key ingredients in bath bombs. When the combination hits the bath water, a chemical reaction is triggered, and you see the fun, fizzy results. Beyond skincare, citric acid is widely used to preserve and flavour food, in medicines and supplements, household cleaners, disinfectants, and more. Read more about it on WebMd here.

Epsom salt (magnesium sulfate):  ‘Epsom’ is an area in England where the salts are found in natural springs. ‘Salt’ in this case means a certain chemical structure. Epsom salt baths have been used for centuries as a folk remedy for sore, stiff muscles, and a variety of other ailments. Magnesium is an essential component in a healthy diet, and a common theory is that when you bathe in Epsom salts, your body absorbs the magnesium in the solution through your skin (transdermally).  However, there is no proper scientific evidence to support this theory. (Read more here). Anecdotally, I find it adds a nice “silky” feel to the water.  

Milk powder: Milk powder and liquid milk contain lactic acid, a mild exfoliant that helps slough off dead skin cells to reveal softer, more radiant skin, reports Healthline. The proteins and fats in milk may also help soften and sooth the skin. Legend has it Cleopatra used to bathe in sour donkey milk. 

Cleopatra readies herself for a sour donkey milk bath.                         Image credit: McGill Office for Science and Society

Kaolin clay: Kaolin clay is a silica rich cosmetic clay with a neutral pH. It is the mildest of all the cosmetic clays and it is suitable for all skin types. It is used in facial masks and cleansers, mineral makeup, and other body care products to draw out impurities, exfoliate, and soften. In our Vesta bath bombs it is used for these nourishing benefits and to help retain shape.

Cocoa butter: is an edible vegetable fat extracted from the cocoa bean. It is made by roasting, stripping, and pressing cocoa beans. Cocoa butter is high in fatty acids and phytochemicals that hydrate and nourish the skin. In solid form, it is dense, harder than other butters, and has a sweet, chocolaty smell.


Shea butter: is a fat extracted from shea tree nuts. Most shea butter comes from west Africa, where shea trees are a native species. It has anti-inflammatory, antioxidant, antifungal, and antibacterial properties, and it’s moisturizing but noncomedogenic. It also has an estimated SPF of 3-4. For these reasons, it has been used for centuries in cosmetics and skincare formulations.


Polysorbate 80: Polysorbate 80 is a gentle, non-irritating water-soluble non-ionic surfactant and emulsifier commonly used in food and cosmetics. Water and oil normally don’t mix, but the addition of polysorbate 80 allows the oils to be distributed evenly throughout a product or mixture. It is used in Vesta bath bombs to prevent the nourishing oils from simply sitting on top of the bathwater. It also helps reduce or eliminate the “ring around the tub” that is sometimes left by bath products.


Sodium Lauryl Sulfoacetate: (SLSA) is a surfactant that produces lather and helps remove dirt. SLSA is  gentler alternative to the traditionally used Sodium Lauryl Sulfate (SLS) and is safe for most skin types, even sensitive skin. It is naturally derived from coconut oil and palm kernel oil. Read more here.


Mica: Mica is a natural stone mineral found throughout the world. The mica powders used in cosmetics are made from ground mica coated with other naturally occurring minerals to add colour and shine.

(Not every bomb contains all these ingredients. Read the individual product listing for specifics.)

Want to learn more about skincare ingredients? There is a great ingredient encyclopedia on Humblebee and Me - a Calgary based DIY beauty blog.

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