Oddly enough I spray my clothes with deet and my arms.
I still catch fish and have some very old Cortland lines still going.
I don't know why someone would spray their hands, flies and fly lines.
Never spray hands, flies nor fly lines or tippets ... anything that can create a source for the smell of the repellents to be smelled/tasted by fish.
If you don't agree, fine.
But I did test.
The chemistry of insect repellents will cause fish to reject the fly.
For the test, almost to scientific standards - same exact place in the water (exactly same place), variety of fish species, each fish very visible for identification and estimated size, exactly the same fly.
Exactly same results.
The very affirming test was having spray remnants from treating arms and hands, etc., get on the fly by manipulating the fly normally to prep it for fishing, and doing so with fingers contaminated with repellent.
The application of repellent did not exceed normal means for, nor volume of, contamination.
In very clear water with several different species, including trout - wild and stocked - the effect of the chemistry of the insect repellent was without doubt repelling every fish species that came up to the fly.
Well hidden, I could see them easily within 10 feet. I could see their heads and mouths easily, and how close each of them got to the fly - carp, chubs, panfish and trout. They were coming to eat the fly, then each fish of each species stopped quickly when they got directly downflow and could smell it.
Each fish of each species was within easy consumption distance, but then they turned quickly away*.
The topic of the effect of chemical odors on flies has never seemed to catch on well in the flyfishing world, but it does matter.
Consider that it is well assumed by most bait fishermen that the odor/chemistry is critical. Not just shape, texture and dynamic.
Personally, consideration is strong that the rejection also can result from using certain materials in tying flies.
Just as well, some chemicals are attractants.
(But that issue as applies to flyfishing should be expected to continue to be an issue of strong discussion.)
*There were no other potential issues, such as "lining" the fish (having the tippet and leader touch the fish), to cause them to turn quickly when they got within a couple of inches of consumption.)
