During a recent conversion about the lower temperature of testicles compared to the rest of the male body I was attempted to find the temperture differential when I stumbled across this wonderful product sold by Babystart Ltd through their website babystart.co.uk

The improved quality of sperm produced when the testes are kept cool is a pretty well established phenomenon (see Schuppe et al 2007) and BabyStart are keen to point this out providing multiple references to proper peer-reviewed journals including Mulcahy 1984 and Schuppe et al 2005. Consequently a cooling patch for the testes seems like a good idea if you are trying for a baby but how does the FertilMate achieve its cooling?

The babystart(r) FertilMate^(TM)Scrotum Cooling Patch is a specially designed hydrogel pad with natural l-menthol used to provide the cooling effect.

The Cooling Patch has a pleasant aroma and a slim, flexible, non-messy format. It is easily trimmed and shaped for use on all sizes of scrotum and comes in a re-sealable bag, with no need for refrigeration.

So according to Babystart the cooling effect is provided by L-menthol. Now we’ve all experienced the cooling effect of menthol whenever we brush our teeth or chew some minty fresh gum but does it actually change the temperature of the skin it comes into contact with?

NO

L-menthol is an agonist for a skin receptor protein known as TRPM8. TRPM8 is responsible for skin’s sensitivity to cold so when L-menthol binds to it the brain is tricked into thinking that that area is cold but it doesn’t actually lower the temperature. A related receptor, TRPV1, is responsible for sensation of heat and can be triggered by capsaicin, the predominent chemical responsible for the “heat” of chilis.

So will these patches work? Probably not, more likely they’ll raise the temperature of your testes by reducing air flow to the skin and subsequent reduction in sweat evaporation. Also as the body is pretty good at feedback loops it’ll probably compensate for the cool feeling by trying to raise the temperature by contraction of the cremaster muscle, much like you sweating in response to eating chilis. It will however probably make your testes smell nice and minty fresh.