Does smoking prevent FFA?

The short answer is that we do not know. A 2017 study by Fonda-Pascual suggested that smoking was somehow protective against the development of FFA and that non-smokers had more severe disease. Other studies, including a study by Dr Messenger's group from the UK did not show this link.

Conclusion

To date, there is no solid information available to suggest that smoking either causes FFA or prevents the development of FFA. Large scale studies will help answer the question for good.
 

References

Aldoori et al. Br J Dermatol 2017.
Fonda-Pascual et al. JEADV 2017.