Do you know why 99,99% of the extant spiders are harmless to humans?
1) Because many spiders (but not all) are evolved to target insect methabolism instead mammal methabolism
2) Because spiders aren't bees. The majority are solitary and small, have a limited body size and can just inject a single tiny dose of its extra-potent poisons.
3) and their tiny chelicers are too small and weak to pierce the human skin until reaching a layer with circulatory system so the poison is stopped by the stratum corneum of dead cells in epidermis and other upper layers of skin
Now lets suppose that a spider could grow indefinitely and make an unlimited amount of poison, like a fungus
And lets suppose that spider poison could be breathed directly and pass from lungs to blood wessels, and acumulated all day like fungus spores entering in your nose
What could happen? shalalala
Maybe nothing
or maybe any insect of any species would be poisoned eventually in presence of spores. They take air directly. Result: collapse of agriculture by simultaneous decrease of suitable pollinators at all levels
or maybe humans would have a new type of allergy, part allergy part nervous poisoning.
People tired of breathing poison all day after a strong rain? People now allergic to a previously harmless and widespread fungus present everywhere?, in its modified and wild forms?