Q I’m a big fan of Durk and Sandy’s Maui SolarMax—it works better than any other sunscreen I’ve ever used. Yet I wonder if they would consider using ethyl alcohol instead of isopropyl alcohol. Isn’t the latter toxic to the body, while the former is not? Even if the isopropyl alcohol evaporates before it can be absorbed into the skin, it’s difficult to avoid inhaling it when spraying the sunscreen on one’s body.

KEN, Redondo Beach, CA

A Isopropyl alcohol (isopropanol) is the type of alcohol most commonly used as rubbing alcohol; it has a very good track record over decades of use. Although there are some case studies in the literature showing toxicity, this results only from ingestion of substantial amounts. In a study with lab animals, oral absorption produced the highest blood levels of isopropanol and acetone (to which isopropanol is partially oxidized in the liver). Skin absorption was far less of a problem, again requiring large amounts. Inhalation alone was of little significance.

As a more recent study found, adverse effects resulting from topical exposure to isopropanol appear to be exceptional in adults with intact skin who are not massively exposed to it. Regarding the possible use of ethyl alcohol (ethanol), the properties of the two alcohols are different. For example, isopropanol is more volatile and thus dissipates faster; this makes it much better suited as a sunscreen vehicle.