34 citations,
July 2010 in “Expert Opinion on Drug Delivery” The document concludes that there is no agreed-upon best method for measuring drug delivery within hair follicles and more research is needed to validate current techniques.
11 citations,
February 2012 in “International journal of pharmaceutics” Ultrasound increases skin permeability but blocks hair follicles.
42 citations,
January 2007 in “Pediatric dermatology” Low-potency steroids can cause serious side effects in people with skin conditions like Netherton syndrome.
52 citations,
February 1985 in “Archives of Dermatology” Minoxidil absorbs poorly through skin, with low risk of side effects at 1-2% concentration.
94 citations,
May 2011 in “BJCP. British journal of clinical pharmacology/British journal of clinical pharmacology” Hair follicles greatly increase caffeine absorption through the skin shortly after it's applied.