Hard water softening effect of a baby cleanser.

BACKGROUND

Hard water is associated with atopic dermatitis (eczema). We wanted to determine if a baby cleanser and its individual components altered free ionized calcium (Ca) in a simulated hard water baby bath. For these studies, an in vitro determination of free Ca in a simulated hard water baby bath, and an in vivo exploratory study of free Ca absorption into skin from hard water were performed.

METHODS

Free Ca was measured with an ion-sensitive electrode in vitro in hard water (100-500 ppm, Ca) before and after addition of the cleanser and/or its components. In an exploratory study, absorption of Ca into skin from hard water was determined in three female participants (aged 21-29 years).

RESULTS

At an in-use dilution of 1%, the test cleanser reduced free Ca from ~500 ppm to <200 ppm; a 10% in-use dilution bound virtually all free Ca. The anionic surfactant component contributed the most to this effect. In the exploratory in vivo study, we measured a reduction of ~15% in free Ca from simulated hard water over 10 minutes.

CONCLUSION

Baby cleansers can bind free Ca and reduce the effective water hardness of bath water. Reducing the amount of free Ca in the water will reduce the availability of the ion for binding to the skin. Altering or reducing free Ca concentrations in bath water may be an important parameter in creating the ideal baby bath.