irritant
Poison Ivy is poisonous because it contains a chemical called Urushiol that acts as a protectant to help keep the plant from being eaten. It just so happens that the Urushiol is an extreme irratant, to not only those that may try to eat the plant, but also to other things as well.
Smoke contains particles and chemicals that can directly irritate your eyes, causing them to become red, itchy, and watery. On the other hand, fog is simply a cloud of water droplets suspended in the air, which is generally harmless to your eyes.
Methylpropional, also known as Lilial, is a synthetic fragrance compound commonly used in perfumes and personal care products for its floral and clean scent. However, it has been identified as a potential allergen and irritant, leading to restrictions on its use in some regions.