Alcohol is an interesting one and the professionals still do not fully understand why it triggers an attack in some cluster headache sufferers, particularly episodics.
I've been looking at the role of nitric oxide (NO) in primary headache for quite a while now. Nitric oxide is an important (gaseous) signalling molecule in our bodies and amongst other things is responsible for neurotransmission, modulation of the hair growth cycle and even penile erections!

NO that originates from the vascular endothelium, neurons and macrophages (inflammatory cells) is also an important endogenous mediator of physiological vasodilation.
Vasodilators such as nitroglycerine (GTN) are converted to NO, which may be why they almost ubiquitously trigger an attack in CH when in cycle. Alcohol also increases NO in the short term suggesting a similar triggering mechanism, but long term alcohol consumption can markedly reduce NO levels, which may help explain its potential as a prophylactic amongst some sufferers (although not recommended for obvious reasons). An alcohol induced attack can also be notoriously difficult to treat, but strangely enough, there have been reports over the years of alcohol being used successfully as an abortive agent, again perhaps suggesting suppression of NO release in the longer term.
Why only certain types of alcoholic drinks trigger attacks for some is a mystery to me but it obviously suggests that some other mechanism or even multifactorial mechanisms may be involved. Red wine is almost always a trigger for me, and although I can drink most white wine, for some reason the Chardonnay grape seems to be a trigger for me, within the hour. Limey-bird insists on buying me Liebfraumilch or Piesporter Michelsberg, which although is pretty nasty tasting stuff, is fortunately OK for me on the head front.
I initially put the trigger factor down to higher levels of sulphites (US = sulfites) in some white wines compared to others, but this is at best spurious. Most red wines also have high levels of sulphites, but more white wines have more added sulphites (as a preservative). Of course, it could just be the varying levels of tannins in wine too.
Another possibility is that the higher levels of procyanidins in some red wine (the stuff responsible for making it "good for your heart") may also affect some people's CH. Procyanidins suppress the synthesis of a peptide called endothelin-1 that contricts blood vessels but it appears to be a complex issue.
Phew! I need a beer after all that. Your shout I believe Brian

-Lee