Both my holistic vets have cautioned me not to over-do fish oil. And to switch it off now and then (don't use one thing exclusively).
Flax you have to be SUPER careful on -- because the human "cold pressed" flax will often produce a nasty diarreha (at the least) reaction in dogs,
The actual fish tends to be the best source -- sardines, anchovy and jack-mackerel. I do that as often as possible. I try not to give a pill supplement more than once or twice a week.
Try something -- at any health store usually they will carry Hylands homeopathics. Try Hylands "Hives" formula -- it's cheap, has absolutely NO ill effects (no sleepiness, no drymouth, nothing like that) because it's a homeopathic.
Just put one under your own tongue -- it's sweet and not at all unpleasant. I offer them as treats. But they are GREAT to help the itchies from the contact allergens. Hylands also has a "Hayfever" formula I alternate with it -- they're easy and without side effects.
The only down side is they don't last long -- you have to give about 4S a day.
Do **not** give in food -- it is supposed to dissolve in the mouth. You can crush the tablet and just sprinkle on the tongue or just let them chew them up. My whole bunch think they are candy.
The other one that really helps is one of Hylands "singles" - "Hypericum". Very soft little low dose pellets -- 3-4 of them. But they reduce that tingle that the histamines make in the skin of the feet -- calms Billy down right away.
But don't touch the pellets -- just tap them onto the floor or into the cap and then just toss in their mouths -- like I said - they are not at all unpleasant.