Oil in Spark Plug well on 1993 Nissan Altima

What would cause oil to leak around the spark plug in to the spark plug well, other then loose spark plugs

Asked by for the 1993 Nissan Altima
Bad valve cover gasket.
Make sure the oil hasn't ruined the plug wires.
Thank you! Will know more when I get the valve cover off.
I have the same car w 191000 mls and the same problem the gasket under the valve cover is leaking both out and into no 1 cylinder (alot) it will cause a misfire if the wires are ok u can use a screwdriver and rag th get most of it then remocve plug crank it a second to blow the oil out then dry and cover the plug and boot in dielectric grease this will help for a while but u have to change the valve cover gasket or ull have more probs
2 more answers
The valve cover gasket gets old and start to crack and allow oil to seep through the spark plug well. Get a replacement valve cover gasket and get some chemical gasket paste (like Form-a-gasket) to help you hold the gasket on the valve cover while you put the valve cover back on, otherwise the gasket will just drop when you attempt to put the valve cover back on. Also make sure to put the nuts in the proper pattern and torque.