Is fabric softener a good hair conditioner? Episode 140

Does blotting oily sunscreen reduce SPF? Emma asks in Gmail…I don’t like the oily skin I get from using sunscreen so I blot off the excess with an oil absorbing sheet. Is this reducing the SPF of the sunscreen? Yes, blotting some of the sunscreen off your face will reduce the UV protection, to some degree. That happens for two reasons: First, most UV absorbers are not water soluble so they’re dissolved or dispersed in an oil phase. That means a high percentage of the active ingredient is in the oil that you’re removing. And less of that active ingredient means less sun protection. Second, good sun protection depends on having a relatively thick, even film of the sunscreen on your skin. In fact, dermatologists specifically talk about sunscreen being wiped away as one of the main reasons to reapply. Apparently this is well studied because I found a paper titled “Effect of Film Irregularities on Sunscreen Efficacy” in the Journal of Pharmaceutical Science. The researchers tested how well different sunscreen films worked and they found “Nonuniform distribution of sunscreen films on skin…account for large discrepancies between naively predicted efficacy and that observed clinically.” In other words, regardless of how good the sunscreen is, if the film isn’t uniform it won’t work as well. The bottom line is that blotting off excess oil is one way to disrupt the film so if you want good sun protection, then you shouldn’t do it. Is it safe to use fabric softe...
Source: thebeautybrains.com - Category: Consumer Health News Authors: Tags: Podcast Source Type: blogs