Some people report benefits, some people say that 5-htp makes things worse.

If the problem is only a shortage of serotonin, then 5-htp is a good choice. But if the problem is that some of the types of serotonin receptors are too active, and some are not active enough, then 5-htp might or might not work, or might be painful. Unfortunately, CH seems not to be simply a shortage of serotonin.

If a person does have low serotonin, that will limit melatonin production - serotonin is the main building block for melatonin. 5htp usually improves my sleep quality. 

The triptans seem to abort CH by increasing activity at the serotonin 1 receptors (mostly 1B and 1D).  Olanzapine and Kudzu block the serotonin 2 receptors (especially 2A and 2C).  Ginger (which is less talked about but a few people here have said it helps) works on the serotonin 3 receptors.

IMO, 5-htp might best be used by episodics out of cycle to prevent a cycle. Some of the receptors tend to increase in number when serotonin levels are low ... taking 5htp in cycle could thus cause problems, while taking it out of cycle might gradually reduce the over-active problem receptors.  This is speculation - some of us might have other factors that turn up the wrong receptors, even if serotonin levels are adequate.