What other allergic reaction to trees are there? Here are some ones I know about.

1. Sycamore trees. There is a dust on the underside of the leaves that can be a respiratory irritant in the spring. It manifests is a hacking cough that no water can put out. People have been known to die from extreme cases. A dust mask is the most simple solution and seasonal climbing of the tree seems to be a way to deal with this tree.

2. Black walnut trees. Here’s one I am allergic to. The leaves make be break out like poison ivy. These trees have a toxin as well, as known by the Native Americans who would pulverize the hulls and toss them into streams thus killing fish that would float to the top for collection. The hulls will also thwart any kind of plant survival other than the black walnut species.

3. White oak pollen. Here’s a new one for me. This tree’s pollen is rated number 3 for asthma sufferers. It’s somewhere about 23% for cause of this illness. I read this in Consumer Reports health newsletter. No other oaks were mentioned. Anyone know this?

I know the tropics have some really nasty trees that cause reactions. Let’s stick to the temperate forests for now. Who knows anything?

Question? Do we include toxic trees? If so, I would like to nominate the Ohio Buckeye (also known as the Stinking Buckeye).
Let's see...the bark and fruit (called buckeyes b/c they resemble the eye of a deer) contain the glucoside aesculin which is poisonous to cattle, pigs, horses and people. The tree usually is smallish w/ extroadinarily weak wood. Farmers often fell them so their livestock won't eat the fruit which even squirrels won't touch.
Why Ohio would pick it as a state symbol is beyond me. The term fetid or stinking comes from the fact that crushing the bark yields a nasty odor.
Of course, my opinion might be biased being a native Kentuckian and all
Randy

In sub tropical florida there is atree called sily oak which is not an oak, but will cause a poison ivy-like rash. I couldn't work with it at all when I lived there.

Sycamore the worst I've dealt with. I get rashes from spruce, juniper and pines. I always keep a dust mask when I'm working with Sycamore (Idaho we have more plane trees. Ive noticed a occasional reaction to walnut. But I deal with them about once a week. I've had more issues with thing living in the trees. Dusts, molds, bird and other animal droppings.

I can attest to the Sycamore tree dust. Once I pruned about 150 feet of photinia hedge growing under Sycamores on a hot August day. The dust got all over me as I was sweating from trying to rake the clipping off of the top of the hedge.I itched all over and my eyes felt like they were filled with sand. The only thing that comes close in my recollection was the time I crawled around under a mobile home for a whole day replacing pipes. We had to remove the insulation first...

The Tangler