Bath bomb

A bath bomb is a compressed, effervescent mixture of baking soda, citric acid, and fragrance that fizzes and dissolves when dropped into bath water.

The fizz comes from the reaction between the alkaline baking soda and the acidic citric acid once water is added. Manufacturers bind the powder with a small amount of oil or witch hazel, press it into a mold, and often add colorants, dried botanicals, salts, and skin-conditioning oils. Because the product is diluted into a full tub, any added ingredient ends up at a very low concentration in the water.

CBD bath bombs contain a hemp extract blended into the oil portion of the recipe. The label typically states the milligrams of cannabinoids in the whole bomb, although how much of that reaches the skin, and whether any is absorbed into the bloodstream, has not been established. These products are marketed as cosmetic and bathing items, and the U.S. Food and Drug Administration classifies them as cosmetics unless drug claims are made. Readers should view them as a scented bath experience rather than a measured route of exposure.