I dont know if it really will... but I dont want to take chances... I use a rag to touch them.... I've seen people in grow videos touch them than wipe them off though... I accidently taped mine... I was high and said ohh let me touch it see how hot it is... and than I said ohhh fuck I'm not suppost to touch it!!!1
I'm pretty sure the reason for not touching them is the same as Halogen bulbs, they will just plain blow up!
I've touched mine and wiped them down before without issue, just make sure that they are cooled before you go about doing anything with them.
Remember, thermal shock and glass don't mix
touching it leaves oils on the glass which makes a hot spot on the glass which can make it weak and shorten the life of the bulb. I use towels to hold mine then twist it in.You can clean them with a denatured alcohol but have to wipe it down real good and let it sit for 2 hours after just to make sure no alcohol is left on it at all.So dont touchj it and forgod sake dont touch it while its on lol