Wuweizi (New York) on 07/27/2016:

I am a 39 y.o. male, 5'11" 160lb, fit and active. Half Asian and very lactose intolerant, I got my first hemorrhoid a couple months ago. It followed tarry stools and toilet straining I attribute to cheap feta cheese that probably had lactose, and also NSAID I took for headache. I believe the toilet strain + NSAID blood thinning caused it. Healed in a week.

Second hemorrhoid occurred a couple months later, with no poor stools, lactose irritation, or other changes I know except for taking 2 capsules of fish oil (each "1200mg fish oil, 360mg total Omega 3 fatty acids DHA EPA") with lunch daily, chewed with food. After five days of this I woke up with what seems to be relapse of the first hemorrhoid. Just woke up with it, didn't even pass stool that morning yet! The fish oil has a warning if one has bleeding problems. This alerted me to the fact that fish oil thins blood and inhibits clotting and blood vessel constriction, and I suspect it causing the spontaneous relapse. I discontinued it and it healed in a week again.