Touching the studio light bulb is not recommended, because the oil which remains on its surface may damage it at high temperatures.
If the light bulb was in contact with skin, how should it be cleaned properly to avoid damaging it?
If the envelope of the bulb is glass or quartz and is not coated, near-pure alcohol and a lint-free cloth will do just fine.
I use Eclipse and Pec Pads because I have them handy, but ethanol, methanol or isopropanol will work. Small bottles can be had from anyplace that supplies industrial chemicals. Avoid what you find on the shelves a drug stores, as some of it contains small amounts of oil which will make the problem worse instead of better.
After cleaning, let the bulb sit in open air for 30-60 minutes to make sure all of the alcohol has evaporated.