I developed this in 2007 after I was taking large numbers of different supplements.
If you search my posts I'm sure you will find what I took.
I too have the Fordyce's Spots in my lips, particularly in the worst affected area in the middle of my top lip. My bottom lip, which very rarely peels, has no noticeable spots.
I have always believed these to be the issue. I believe that the supplements I took caused my sebaceous glands to malfunction, possibly hardening the sebum, meaning it now blocks sebum from reaching the outer layer of the lip.
Sebum is what keeps skin elastic and waterproof and these are the two things my lips no longer are since I developed the condition.