I've been really curious about this so I googled it. Not much reliable data but it's worth investigating.

Transdermal absorption

THC and CBD are lipophilic compounds (i.e. they like fat, but water not so much). Compounds that easily penetrate skin layers, are ideally moderately lipophilic, less lipophilic than THC and CBD. Therefore, bioavailability of cannabinoids such as THC, delta8-THC, CBD, and CBN for transdermal absorption is expected to be low when no absorption enhancer is applied.

There are some methods to improve absorption through the skin layers, including temperature changes, applying voltage pulses, or ultrasound. Another method is to dissolve compounds in a solution of penetration enhancers. These will increase penetration and thereby absorption by interacting with the skin’s lipids. They could be incorporated in products such as dermal patches to increase the absorption rate of THC and other cannabinoids. There are not enough studies to conclude whether THC and CBD effectively penetrate the skin for it to be of comparable effectiveness as an oral administration. Clinical trials need to be done.

Maybe temperature changes are enough to encourage the THC/CBD to absorb?